Johnny Luken wrote on Sun, Oct 14, 2012 12:35 AM EDT:Excellent ★★★★★
A pretty playable subvariant would be with both boards full, and ordinary moves, starting and ending on the same board, by necessity, legal.
You could even adapt the mechanic for higher dimensional games, with layers of boards, with the rule that for a piece to move legally from one board to another, the move would have to be legal on all intermediate boards aswell...