In essence, I can't see any problem in doing this but if you are using an ESC (electronic speed controller) it would be preferrable to use one with a BEC (battery eliminator circuit) and use that to power the receiver.
In case you don't know, a BEC circuit is designed to do that very thing. You plug the ESC into the receiver and it then powers the receiver hence eliminating the need for Rx battery.
Hope this helps,
Scottie