Thank you for the feedback! I think some of these are already there in some form, they just might need some tweaking:
1. I haven't seen this as a problem, but it shouldn't be too hard to make the highlight more visible. Added to my todo -list.
2. I have intentionally limited the menu control to certain players to prevent "menu fighting" as multiple players try to navigate in menus at the same time, either accidentally or intentionally. For keyboard, it's the rightmost player as arrow keys/enter is the logical choice for menu controls. Selecting should work with that player's fire buttons (right shift/ctrl) too.
3, 4. You should be able to navigate the menu using the first gamepad's dpad buttons and X/A button. The menu and controller help overlay should toggle by select/guide and start -buttons. Does this not work?
5. This is already on my todo -list (as low priority item, though).
6. The reason for not using the "triggers" is that depending on gamepad they can be digital buttons, analog triggers or completely missing. One set (the upper on XBox/PS controllers) of trigger buttons is (almost) always present and digital.
The controller remapping question comes up often, but it's unlikely that I would add that. I have instead tried to add alternative buttons for things that annoy people the most. The reasoning is that this is supposed to be a party game where players change often. If the controls could be changed, most of the time would be spend in menus tweaking controller settings instead of playing.
7. I'm not sure if I understood the problem.. Right stick only turns without accelerating.