[Corinthian]

Funny you should mention that Bat/man, because the water global: "The Maelstrom" already works like that. Although most gems(15) you get are water gems, you also get 5 astral pearls and one of each other gem types I think.

Also gem gen globals are not as destabilizing as gem gen items as they are not anonymous and they can be stopped much easier. Furthermore, a nation with many globals might get ganged upon because of it. And because there can only be one global of the same kind in a game it can shake up a stalemate.