To implement owner choosing the promotion in Zillions, what you can do is to have another move-type with first priority, giving the pawn a move with that priority that is only valid on the back rank, and then it has the move to transform into the other player's "PromotingIntoQueen" or whatever (the pawn has four moves with this priority); that piece also has the priority move, which just changes into the opponent's queen or whatever it promoted into. Therefore the turn order is working in the correct order.