On this board, the Rook can bring any 1 (one) other friendly piece along with it, but the player must balance the other piece atop the Rook and push the Rook along the board to its destination. The Rook may at no point leave the game board. If the carried piece falls off at any point, it is forfeit. The player must also imitate the noise of any internal combustion engine while moving the Rook.
Any number of models that can fit or balance on the Battlewagon can be carried by it. Any models which fall off during play are judged to have actually fallen off and the normal rules apply.
I would love to see professional chess players give this a fair chance. The clock could stop when they declare their move verbally (ensuring that the game doesn't devolve into an endurance test) and start up again for the next player upon the move being completed.