Shuju Shogi

Shuju shogi (種々将棋) is a shogi variant I invented, played on a 15×15 board with 3 different zones, each paying homage to one of the 3 popular shogi variants of olde: dai shogi, chu shogi, and sho shogi. The central 9×9 zone has the exact setup as used for sho shogi, with the notable drunk elephant right in front of both kings. Around this zone is a larger zone, wherein most of the pieces common to dai shogi and chu shogi are placed. In hand are an assortment of weak pieces, most of which are unique to dai shogi.

Another noteworthy difference is how rule enforcement works. Indicated by the dashed blue line are the promotion zones. In the sho shogi zone, sho shogi rules apply. In the chu shogi zone, chu shogi rules apply. In the dai shogi zone, dai shogi rules apply. Based off in which zone a piece enters, the piece promotes however it would in that particular game. So a silver would have the option to promote to a gold in the sho shogi zone, but it would have the option to promote to a vertical mover in the other 2 zones.

Lion trading rules only protect lions in the chu shogi zone. A double capture of a significant piece in another zone is not sufficient to make legal the capture of a protected lion by an enemy lion, if that protected lion sits in the chu shogi zone. 

All pieces captured in the sho shogi zone are taken in hand by the capturer. If a player captures a promoted piece (in the sho shogi zone), they have the option to take either the promoted or unpromoted side in hand. In both other zones, captured pieces are permanently removed from the game, with the exception of pawns and go-betweens, which are taken in hand. Pieces in hand can only be dropped into the sho shogi zone.

Generally, pieces can enter and exit zones as they please. There are two exceptions. Royal pieces (king and prince) are allowed to change zones, but only if the player sacrifices any three pieces of their choice, from on the board or from their hand. This sacrifice must be made each time a royal piece changes zones. These sacrificed pieces are permanently removed from the game. Also, each time a lion moves (or is dropped) and ends its move inside the sho shogi zone, that player must forfeit any two pieces of their choice, which go unchanged into the opponent's hand.

Play begins with 2 moves reserved for dropping both go-betweens, one at a time. During this initial placement phase, go-betweens must be placed 1 rank in front of a pawn. This is the only time it is allowed to drop pieces outside of the sho shogi zone. Passing is allowed. After this, play continues normally.