Not only is this my favorite game on the PS1, it wouldn't be a poor speedrunning candidate either. Obviously it's a bit of a blow that the long intro and recruitment cutscenes can't be skipped, but on the other hand, most of the game is completely optional. I haven't actually done any test runs yet, and I won't have PS1/2 access until the fall, but I'm throwing this out there to see what anyone thinks. I heard a ballpark figure someone gave of 8-12 hours or so, but I know that is way off.
I am thinking the fastest route would be Easy B ending, excluding the C ending of course. In Easy, you are limited to less skills, characters (not an issue), equipment, and level 1 items (no Creation Gem/Jewel). However, the enemies are a bit weaker and your guys actually come with levels (also probably not as issue since you'll be sticking with early Arngrim, Jelanda, etc). You do get Guts and Auto-Item, and you can receive from Odin and divine yourself decent enough equipment.
The A ending is much cooler, so of course it deserves a run in a separate category, but B has to be faster. For A, the killer is getting Mystina, which requires a whole 'nother dungeon (Tower of Lezard Valeth). Luckily, you get Creation Gem and then Jewel from that dungeon, but I can't remember what would be useful to make by that point. You'd also have to watch a lot more cutscenes, including Lucian and Mystina recruitments, Lucian transfer, Loki stealing the Dragon Orb, etc. (The one advantage is the final dungeon is a lot shorter.) So if I or anyone else were to do this, he/she would probably try the B ending first.
I don't know how many optional dungeons I would do. I would get Arngrim's Dragon Slayer, so probably dungeons with dragon bosses like Dragoncastle Caverns, and fighting Dragon Zombies inside Caves of Oblivion sounds like a good idea too. Normal has a couple more dragon bosses, but dunno if that's worth enough.
About the fourth character, ideally it would be someone with useful equipment you can get afterwards, like Nanami. But really, it would most likely come down to figuring out who has the shortest recruitment cutscene. I think that when you get characters is set when you start the game and not when a chapter starts, so restarting to get Chapter 2 Nanami would be quite annoying. Finally, I am a big fan of mages in this game, but 2 mages is a little suboptimal as you don't get to fully exploit either Sap Guard/Might Reinforce or Spell Reinforce. Chapter 2 Janus and a Raven Slayer might be another option.
Ok, that's it for now.