I've got local co-op working in Match Shot Chimera, for up to 4 players!
Presently it's a "carry your kids" mode. Player 1 has the usual multiple hearts while co-op players each need resurrecting any time they're hit. Sit in a rez circle for a while or fetch an insta-rez item dropped by matching 3, and your co-op partner(s) will get another chance.
It's certainly OP, but that's kinda the point!
I've also tested a "die with your friends" mode where everyone shares the same health bar. That's lower priority at the moment, but I'm open to adding it later!
My big move is mostly done now. This was a great way to get back into the thick of development. I'll be getting back to work on the rest of the next alpha now!