totaly,
That is the EXACT reason you don't need hand wheels on a cnc'd machine.
I read many threads about the backfeed problem trying to use ballscrews in a manual mode.
I have found the use of either MDI or continous jog to be the answer and haven't looked back!
I am in the process of making my lathe cnc and it will NOT have handwheels. There is no need and if I want some quick feed, there is jog in my control software and if I want to be accurate, there is MDI!

Just my .02

Bubba