I personally wish this was an Other permanent of some kind, so that ALL mono decks could join together in the POOPING ON RAINBOWS REVOLUTION!
As it stands currently, Rainbow decks could grab this card to poop on a duo or trio, and the the duo/trio would not be able to poop back unless it had
itself.
This is part of why it's so hard to properly do this "pooping" thing. Black Hole is available to ALL rainbows, but only available to monos/duos/trios that specifically include Gravity.
Regardless, I support any incarnation of this card making it into the game. VIVA LA POOP REVOLUTION!