I have played chaturanga for four players and think that it would be a good game to add to BrainKing. Team play is a lot of fun.

There is a large chess variant for two players called Big Battle (see chessvariants.com) that is played on a 10x10 board that would be a great addition. Not only is it fast-paced (a surprise on the larger board) but well balanced, like Gothic Chess.

It is not a mere variation on the theme of Gothic Chess, though; and on the strength of that and the popularity of chess variants on the site, I think that it would be good to give it consideration.