First of all I will emphasise that there are a lot of issues that should be addressed before adding content which doesn't address those same issues. That being said I'll go through each of your points with my own take.
1-4. The idea of fortifying a village is not historically inaccurate. But it doesn't quite sit right to have every village possibly become a castle. I wouldn't be against the idea of allowing village upgrades though (such as palisades, platforms, a barrack or even a personal home/manner).
5. The idea of makeshift defences wouldn't be beyond the scope of the game I think, whether it would be fun in practice though I'm not sure. However, the command tent seems a little odd, thematic sure, but due to the pace of battles there really wouldn't be much use of going all the way back to your tent, to what I assume would be to go into RTS camera mode.
6. Sieges already have these "stages" in a sense. However, sieges do need a lot of work (as I've suggested in another thread).
3?. I think cavalry are already mechanically strong, I do think commanding them to charge certain areas (as well as an RTS camera in the base game) would go a long way to making cavalry more tactically viable in more situations though.
4. Yes, this would be a fine addition. Currently the only way to do that is to hold fire + fire at will (at least as far as I'm aware).
5. Fire arrows for what reason? Fire arrows as a primary battlefield weapon is something from pop culture rather than historical records. Lindybeige does a good video on why fire arrows were not a thing and that actually, they don't make logical sense in an open field battle.
6. Yup, it's not a bad idea.
7&10. You've been playing too much skyrim. That being said, this could be a funny but very niche mod I guess.
8. I've not tried playing with that mod yet to really see how good/bad the extra gore is, but I don't think it's really needed in the base game.
9. Combat feedback in what sense?
11. I'm not sure what this means.
12. Haven't used either of those mods to make a valid comment.
14. There probably should be more dialogue/reactions/content within towns/castles/villages. I'm not sure about non-military saluting (even military saluting is questionable whether it's historically accurate on not). And I'm not sure why you'd want to arrest a poor citizen (both thematically and mechanically).
