I can see nothing wrong with the Flaps being lowered or what ever you want to power up, or move during the push, as long as you inform the head set man what you are about to do.
Technically speaking he is in charge on the push back, if he calls brakes on, you apply the brakes, not 40 seconds later when you have wondered what the hell does he want them on now for.
It's the same if he calls out cut the start or shut down on an engine, he can see what you can not, so learn to trust the guy's wearing the electric hat and may be they will trust you not to run them over.
