That's cool that you've got full game categories etc. I can see you folks put a lot of thought and hard work into getting that online.
I think the major issue is that this board doesn't represent the majority of the speedrunning activities the community is interested in.
Single monster fights (ie via investigations) are the easiest entry point for someone who wants to get into running Wilds.
It's also easier to review submissions for the moderators. The game time at the end is all you need.
It's where the community is at - if you look at all speedrun videos on YouTube that's what people do and want to do. This board should reflect that.
I've been there as a major game moderator on speedrun - I know it seems impossible. But I emplore you to find a middleground ruleset for single fights. Investigations should be an entry point part of the speedrunning challenge will be to practice it against any difficulty and then execute against a low difficulty investigation with your limited tries. It becomes up to the player to determine best spawn point by camp. The question mark on environmental use - make a call.
I would put up a draft ruleset for single mon on a MH Speedrunning Discord and have the community discuss, many brains are better than one. It's how we did it with Hades.
Haven't seen a speedrun discord for MHWilds though - maybe a central place for the community needs to exist. Unless I missed it.
You can setup game version based leaderboards, to cover major patch and balance changes.
eg how we ran it with: https://www.speedrun.com/hades .