My starting RB is a 3 down back, so i have no use of overrides. But i would not like to have the ball thrown to my #2, i would rather see my 3 if #1 is out due to fatigue. That's were a depth chart by formation could be great.

just to clarify, your saying:
RB1 - good for run or pass
RB2 - good for run
RB3 - good for pass
and what you want is a way to use overrides for your RB2(formations you primarily run from) and RB3(formations you primarily pass from) only if your RB1 is fatigued/injured?

Yes :)