[KenWittlief]

Interesting idea.

I dont think battery voltage should matter to your PID loops - they look at what the robot is actually doing and adjust accordingly, so they should respond correctly inspite of the other variables the robot is dealing with (carpet friction, motor temp, obsticals in the way, battery voltage...)

but for #1 on your list, if you are running auton open loop, then you could compensate for low battery voltage