I think actual game play would work best with felt and velcro.
Step one: three and a half pieces of paper. Fold.
Step two: color. And color. And color. Oh god so much coloring. Black should be opposite black.
Step three: mobify.
To be honest, my original motivation was my feeling that pawn promotion is a bit of a copout. This seemed the most interesting way to do away with it.
P.S. This is basically what I'm envisioning for the diagonally looping bishop variant. Just imagine eight columns with the usual two color pattern.