Well I would like the abysmal UI, text and window sizes, and unpolished mouse support areas addressed first.
Agreed, this is of the utmost importance.
Off the top of my head, the next priorities are:
1. Hotkeys for favorites. (Until we have the tools, it's tough to say if this is even possible).
2. Bugfixes in menus for rebinds. (I play ESDF, but some menus still display the default WASD hotkeys for actions).
Low priority:
1. Ability to switch between gamepad/joystick and mouse without exiting the game. (Possibly difficult).
2. Add separate hotkey for exit menu (instead of TAB being required).