OK, here's the next WIP, up to entering Belgen:
http://dehacked.2y.net/microstorage.php/info/852798252/Lufia%20%26%20The%20Fortress%20of%20Doom%20%28USA%29%28test1%29.smv
Yes, I forgot to rest at the Inn before entering the Ghost Cave, and as a result there's more waiting during the fight with Phantasm than necessary, including a particularly long wait. Nevertheless, it demonstrates that my idea of spamming Mid Arrows and manipulating Phantasm into doing non-offensive stuff works.
I've also done testing after that point (playing in realtime for the most part and with the RNG locked most of the time to prevent random battles, then unlocked during boss battles).
For the next two bosses, when I did some tests, it seemed that spamming Big Arrows and manipulating them into doing non-offensive actions works.
It's when I fight against the Guardian that I'll want to level up. Since the Guardian doesn't move during battle, I can't simply wait until he does something non-offensive. To manipulate luck I have to either change how much I wait before entering battle or what actions the characters do.
Fighting the Red Cores doesn't seem to be doable at the levels I'll be at at that point. However, Mimicker can be done, though it's kind of a pain. Fighting the monsters around Frederia yields about the same amount of experience (in fact, they can yield somewhat more), and with the right groups of enemies they're very easy to kill using Ex arrows.
For this first phase, I think I'll want to level up at least until Lufia has Stronger, possibly more. By the time you aren't getting at least one level-up per battle (somewhere around level 18-20?), roughly speaking, you can fight the Red cores without getting your butt kicked. In this case, I try to get an enemy combination with Red Core(s) and one other group of enemies (since I've never seen Red Cores appear by themselves). Kill the other group, probably with Ex Arrows, then manipulate it so that all but one Red Core run away, unless my characters are doing particularly well against Thor. Then get that one Red Core. Level up in that way at least until Lufia has Boost, since that spell is incredibly helpful. I'll have enough money that, combined with the Engage ring and selling items I've picked up, I can outfit my characters with far better equipment, especially since I skipped several generations of equipment for the most part.
At some point, probably once I can fight the Green Cores, level up at least until Jerin gets Mirror. I have the memory locations that indicate how long it is until certain characters have their mirrors expire. That makes it easy to have Jerin keep mirrors on the characters all the time, so that all Sinistrals except for Gades are a piece of cake.
So yes, there will be some grinding, but FAR less than the usual amount due to taking advantage of enemies that yield particularly high amounts of EXP that usually run away. Sort of the Lufia equivalent of Metal Slime.
EDIT: Here's an SMV with the Follower defeated. Much easier battle since my HP was actually healed and I now can use Big Arrows.
http://dehacked.2y.net/microstorage.php/info/522078640/Lufia%20%26%20The%20Fortress%20of%20Doom%20%28USA%29%28test1%29.smv