Using 2 HUDs will allow assigning from one to the other. I'll look into it - I thought there was an option to block assignments in general, will add one if it's not already there :)
6) In game events, yes, in battle events, you only have those available that are part of the action (user/target).
Probably better if I just add new steps to change the player like using the member change keys :)
7) No.
Usually, you'd use the controls defind for changing members to do this kind of stuff, not use an event ...