(zzo38) A. Black wrote on Tue, Dec 10, 2013 05:42 AM UTC:Excellent ★★★★★
Perhaps a way to make "invulnerability" would be that: king, queen, and chancellor cannot be attacked by spinach moves longer than a sequence of five normal moves, unlessthe moving piece is a king, and any piece that has not yet moved cannot be attacked by spinach moves longer than two, unless the moving piece is a king or pawn. (This results in rules more complicated than you intended, but is another possible subvariant anyways.)
It looks like a pawn can move two spaces forward from its initial position with a spinach move, in order to avoid being captured by en passant, although this doesn't seem it would be a very good move in most situations (although maybe there is one; make up a chess problem if you know of one such situation).
Perhaps a way to make "invulnerability" would be that: king, queen, and chancellor cannot be attacked by spinach moves longer than a sequence of five normal moves, unlessthe moving piece is a king, and any piece that has not yet moved cannot be attacked by spinach moves longer than two, unless the moving piece is a king or pawn. (This results in rules more complicated than you intended, but is another possible subvariant anyways.)
It looks like a pawn can move two spaces forward from its initial position with a spinach move, in order to avoid being captured by en passant, although this doesn't seem it would be a very good move in most situations (although maybe there is one; make up a chess problem if you know of one such situation).