Alright, boss TAS analysis time. I'll be listing as much as I can understand with my limited Japanese knowledge (thank God mostly everything is in katakana) and as much information as I can about everything I list. This is all off the top of my head, so there may be some misinformation.
I've decided I'll be posting these in parts instead of one massive post. It seems easier to take in this way, plus it'd be easier for me to provide clarification if necessary. It'd be easier for me to edit in the future, too.
A couple things to note in advance so I don't have to point it out every boss: It appears that all random encounters in the game are avoided, so level and stats will be at a minimum throughout these boss TASes. As for the bosses themselves, Universe difficulty gives all enemies a much higher chance to block damage, so these might end up being the fastest strategies for Universe. Since a complete run is most likely going to be on Earth, that's where I'll be aiming my improvement comments.
All Galaxy and Universe do is make the enemies and bosses harder. The strategies and battles would be the same for the most part as it stands.
These are not all the required battles in the game, I'll be pointing out unrepresented forced encounters where I remember them.
Two last things: One, some of my proposed strategy changes may require further explanation of the game mechanics to make sense, which will come in another essay-length post in the future. Two, every character in the game is optional except for Claude and Rena: When I reference a character "joining automatically", I mean they ask to join during the story with no sidequests or requirements. They can (and usually should) be refused.
BOSS ONE: ALEN-TAX
Battle starts at ~1:30 in the encode.
Rena is at her starting level (1), wearing a Knuckle (her default weapon) and Leather Armor. Game time is 0:32, maybe a little above average for a TAS.
The Leather Armor I assume comes from one of the chests outside Arlia's General Store. It's not necessary at all and would waste about 4-5 seconds.
Alen-Tax isn't the first forced battle in the game, but he's the first one that requires a strategy. The strategy the Nico TAS uses is solid: Pin Alen between Rena and Claude to prevent him from wandering off and to keep him getting damaged. The main problem I see here is mostly leaving Claude to the AI, which attacks slower than a human-controlled character would. A TAS could easily take advantage of switching characters extremely quickly to dish out as much damage as possible.
In fact, I think R2 will instantly switch between the last two characters you controlled: You can switch to Claude as the battle begins and hit R2 to switch back to Rena, and then simply hit R2 to switch back and forth to keep them both attacking at full speed.
BOSS TWO: AZAMGIL, SHIELDER x4
Battle starts at ~3:15 in the encode.
Dias is at his starting level (35), wearing a Marvel Sword, the Brigandine armor, a Fine Shield, a Leather Helm, and the Mud Boots (which are required to advance in the Heraldry Forest).
Rena is at level 3, wearing a Sorceress Knuckle, an Amber Robe, a Buckler shield, a Leather Helm and Leather Boots.
I'll put this right out there: You wouldn't have the Marvel Sword at this point in a TAS. The steps you have to take to get it outweigh the time it would save in battles: You need to actually do some grinding, pick up skills from different towns on the map and use the SP to unlock the Pickpocketing specialty, and then you'd need to manipulate pickpocketing the Treasure Chest from an Old Man in Mars, and THEN you need to manipulate actually getting the Marvel Sword upon opening the Treasure Chest. It's a lengthy process, to say the least. I believe the rest of Dias' equipment, barring the Mud Boots you automatically receive, is his default equipment.
The Treasure Chest, to give a quick explanation, gives you three random items from a large pool upon use. These items can be anything from Fanzines to disc 2 weapons. The pool contains quite a lot of good equipment for most characters, and the Marvel Sword is arguably the best weapon you get out of the Treasure Chest.
Rena's Sorceress Knuckle is also from the Treasure Chest, and getting both the Marvel Sword and Sorceress Knuckle is exceedingly rare. I've tried countless times in the past to no avail, though it's certainly possible. So again, you wouldn't have either insanely powerful disc 2 weapon for the TAS. As for the rest of Rena's equipment, I don't think she'd be throwing herself into battles too often after this one, so I'm a bit iffy on whether or not it's worth giving her defensive equipment. It'll be looked into at some point.
This presents a strategy problem: A lot of these battles use these powerful weapons, meaning I can't properly judge how the strategies would work with normal weapons. I'll do my best, here.
Game time is 3:33, which would be most of the way through disc 2 for a TAS. Oddly, there are 6 encounters listed when I can only think of 5 forced encounters up to this point... Even then, Rena remains the same level she got to after Alen... which implies that she was either killed off or not in the party for the Bandit encounters in the Heraldry Forest... which makes no sense. I'd rather she stuck around to soak up the free EXP anyway. Those three encounters are utter jokes with Dias being level 35, by the way.
This battle is unique to Rena's story (there's a different boss in Claude's story) and as such it's not one I'm all that familiar with. The strategy here... might work without the powerful weapons. I feel like switching characters is the best course of action here as well: Dias is still probably best off sending out Air Slash after Air Slash, they're quick and much faster than his normal attack. Rena's purpose might be more suited to luring enemies closer to Dias to save frames with each Air Slash, though he has to stay long range (as indicated by the game), but she can attack too.
Again, not being familiar with Rena's story, I'm having a bit of trouble with a proper strategy for Dias.
VISSAYER x3
I have so many problems with this battle.
One: It's completely optional. Two: Ashton is there. Three: Celine is there. Four: Ashton has the Lotus Eater, which is another Treasure Chest item. Five: WHY IS ASHTON THERE.
Okay. Let me explain.
Before sailing off to the Lacour continent (where this boss battle takes place), there are two men talking in the port town of Herlie. They mention a two-headed dragon back in the Salva Drift, which is all the way back across the continent of Cross. To recruit Ashton, you have to talk to these two men, then go back to Salva, re-enter the Salva Drift, watch a long cutscene where the dragons merge with Ashton because Claude is a douchebag, and then of course you have to travel back to Herlie to take the boat. This is roughly a 10-20 minute detour, as I stated in the OP, but there's a second downside: Every individual character recruited means more dialogue throughout the game, so recruiting Ashton means you lose even more time throughout the run.
That's my main problem with these TASes: Ashton is present for most of the battles when there's absolutely no way he'd ever be recruited in a speedrun, meaning a lot of these strategies just wouldn't work the same way. Don't get me wrong, Ashton's a great character, but he's not nearly great enough to save the time he takes to recruit.
Celine being present for the battle also makes no sense. Sure, she joins automatically during the story and thus technically takes no time to recruit, but as a mage all she really does is sit there and soak up EXP at the end of the battle. She's also one of the... eh, talkier characters, shall we say, so recruiting her means more dialogue boxes.
And yes, this battle is optional. You can obtain what you need from the Sanctuary of Linga without ever knowing these guys are in there. You're sent in there to get a rare herb, and there happen to be two choices: The Clarisage and the Dillwhip. The Clarisage is not only faster to get normally, it doesn't require fighting these guys.
So there's no reason to analyze the battle. In fact, even the TASer knows it, as the next battle doesn't have any of the level gains obtained from the Vissayers. Next!
BOSS THREE: HARFAINX x2
Battle starts at ~6:05 in the encode.
Leon is at his starting level (30), wearing a Dictionary, an Amber Robe, and Suede Shoes. To my knowledge, this is his default gear.
Rena is at level 8 and is wearing the same equipment as the Azamgil battle: Sorceress Knuckle, Amber Robe, Buckler, Leather Helm, Leather Boots.
Claude is at level 4, wearing a Marvel Sword, a Brigandine, a Fine Shield, a Banded Helm, and Plate Greaves. If memory serves me correctly, the defensive equipment comes from being supported by the Counterpunch weapon shop during the Lacour Tournament of Arms, meaning it's basically free.
Celine (who has a purpose in this battle) is at her starting level (8), wearing a Silver Rod, a Silk Robe, a Leather Helm, Pin Heels, a Rainbow Diamond and the Bandit Gloves. Considering I never use Celine, I have no idea where she gets the Silver Rod. The Bandit Gloves come from Herlie or Hilton, I believe, and they're only useful for the Pickpocketing specialty which ultimately should see no use during the TAS. Also they're 40000 FOL. The Rainbow Diamond would be better off Metalworked into an Atlas Ring and equipped to Claude...
...because Claude should have the Eternal Sphere for this battle. The Lacour Tournament of Arms happens before the Hoffmann Ruins, so you'd have the Sharp Edge, meaning you could manipulate the Radar skill into giving you the two Mithrils you need to Customize it up to the Eternal Sphere. The Eternal Sphere plus an Atlas Ring on Claude means he should pretty much be able to solo the battle with absolutely no effort.
Another quick mechanic explanation: Claude's only level 4 for this battle, meaning he'd have gained less than 10 SP over the entire course of the run up to this point. How does he get the SP for Customize? By unlocking talents. Talents are innate "abilities" that each character has that allow them to be more successful when using certain specialties. For example, the Sense of Taste talent helps the character succeed more often with the Cooking specialty.
Characters can unlock talents randomly upon using their specific specialties. Using the above example, a character may be able to unlock the Sense of Taste talent whenever they use Cooking. Here's the kicker: Every talent you unlock on a character gives that character 100 SP. All you need is enough SP to unlock a specialty you don't have the attached talent for.
I'll repeat this in a future planning post, but we want characters to start with as few talents as possible, as the bulk of our SP gain will be from unlocking talents. The first huge talent unlocking session will most likely be in Hilton, just before departing for the Hoffmann Ruins (where this battle takes place), so... hey, it fits in here.
Back to the battle! Claude may be able to solo, but to save as much time as possible (and to keep everyone alive) he needs backup from at least one other person. In the Nico TAS's case, it's Celine. Celine's purpose is to use Thunderbolt to interrupt the other Harfainx from using Thunderstorm, which is a lengthy magic spell that does a hell of a lot of damage to the party. In short, one Thunderstorm means game over for the TAS.
Now to analyze the actual battle: It's painfully slow, though keep in mind that Universe doubles enemy HP so it'd be much quicker on Earth. The first thing Claude rightfully does is use a Silence Card on one of the Harfainx: This prevents a Thunderstorm. Then... everything slows down... except Claude, who uses a Skanda Compress (I think?) and speeds up dramatically.
Leon is useless in this battle. Black Saber may look like it does a lot of damage, but that animation takes way too long to sit through as many times as it happens. Claude with Eternal Sphere and proper accessories (Atlas and Berserk Rings) would do... maybe 2-3x that damage with a single swing. Celine, as I said earlier, wouldn't be there since she wouldn't be recruited. The only purpose she'd serve throughout the game would be to interrupt spellcasting, but that can easily be done with fighters by just having them attack different enemies.
So strategy-wise in the TAS, there would be a maximum of three people in the party: Claude, Rena, and Bowman. There'd need to be some tests done to see if Bowman saves more time in battles than he adds by being in the party: With a good equipment loadout he's actually a really damn effective fighter and would shorten late-game boss battles significantly, plus he joins automatically. I'll assume that Bowman is recruited, just because I have a feeling it'll be faster in the end.
Basically, the battle would go somewhat similarly to the Nico TAS: Silence Cards would need to be used right away to prevent immediate Thunderstorms, Skanda Compresses would need to be used to keep up with how fast the Harfainx are, and both Harfainx need to be attacked at the same time to prevent further Thunderstorms. Character management would be essential to prevent the low-level characters from getting wrecked, especially since Rena lacks a good heal at this point and it wouldn't matter anyway since you'd get one-shotted.
Claude would attack one Harfainx, leaving Bowman and Rena to attack the other, whittling down its HP and preventing it from casting Thunderstorm while Claude mops the floor with the first one. Eventually Claude would come back around and provide the finishing blows.
That's all for now, I'll write up another few battles tomorrow. I apologize if there's any information that isn't explained coherently or paragraphs that suddenly cut off: I jumped around a lot while editing, and also took a few long breaks, so it's definitely possible I left some unfinished thoughts. I'll take another look at everything once I wake up.