Think the big problem would be synchronizing the BB leaving the barrel and the recoil action, as the airsoft motor takes so long to wind up before releasing. IIRC, somebody said the VS tank airsoft guns have a switch which is triggered when the round leaves the barrel. If you're using Heng Long electronics, it should be possible to rig this switch to trigger the recoil action, just a matter of finding the right signal on the board.

D.