Pieces would demote on capture, just like in Shogi. But my idea says
pawns cannot be dropped at all, only spawned, so this won't make a
difference. Kozune's (promoted pawns) cannot be dropped. I would make the
Kozune the back-side of the pawn tile, like the Tokin is on Shogi.
The promoted pieces are reduced to Pawns and discarded(since the Sho can
spawn them anytime). This was what I was thinking of as well, maybe I just
didn't write it and it is confusing.