Yeah, the level 12 grind is a huge detriment to anyone wanting to play the category; ending runs off by grinding for hours on end doesn't sound like anyone's idea of fun. That's a big reason why I'd rather have 100% be a sort of 99% instead where you gather all fossils and go through all major battles. Leveling up all characters to max rank is absurdist.

I can't remember all of the available postgame battles, though, nor what all they give. We'd need a list of that and some decision on which ones are important.

Would something like Two Heroes% be doable in new game without deleting the old file?

If not, it would still be doable to protect your progress by dumping it, which should be fine for all 0 people running the category.

I don't really think that individual-chapter runs should be done with prescribed warrior lists beyond what might be useful for routing for Two Heroes% (not to run it, but to give a sense as to how fast it would be humanly). Initial warrior lists would only be easily doable on Emulator, as the only save file that can provide consistent initial warrior list runs of stories would be one with no warriors present in that story preregistered in Gallery. It actually might be doable through selecting "no" at the end of each story when asked to save warrior data, but setting up the save file sounds rather tedious. Still, though, I might be able to work through setting it up at some point then uploading the save, at which point anyone with an emulator or a modded DS would be able to run such a category with minimal setup.

A no-holds-barred approach would be easier to set up without deleting one's file, but on the other hand would involve long lengths of time getting the Pokemon one wants and would probably have a lot of overlap in terms of viable Pokemon to use.

Could we possibly make a category that's "All fossils integrated, all relevant battles completed" instead of 100%? Guhnash grinding seems exceedingly tedious and 80% ignores the majority of fossils in the game.

It might be better to describe the category as "Revive/integrate all fossils, obtain all vivosaurs except the 5 chickens".

100% is basically getting everyone up to level 12, considering that that's how you're supposed to get the chickens. That being said, the current 100% run we have doesn't have many of its vivos up to 12, yet still has all 5 chickens; I don't know for sure, but it seems likely that either our understanding of the requirements for chickens are horribly wrong (which would make some sense given how undocumented the game is) or there was some use of the Fossil Cannon.

I can't remember if it's possible to send vivos from Champions to the original, but if it is, that was probably used in their run without them realizing it, considering that it was a casual run for them.

There are Lunatic+ "speedruns", don't know exactly how optimized they are, but it's possible to very consistently beat Lunatic+ without resetting. The main problems with it would be the long run times and the sheer amount of on-the-fly routing involved likely pushing away most people. Not sure how much the time could be improved.

This is a playlist rather than a single video, and later runs get the time to around 8 hours and change.