Thinking about it some more, I really do love the chess theme MCH originally had, and there's definitely room to play with that too.

A Knight turret could provide a minor defensive buff/shield to the party, while Promotion could greatly enhance a turret to "Queen" with an appropriate offensive/defensive application. Give the turret a "Checkmate" ability to provide a % damage increase for the party (like a reverse Hypercharge) that uses MP (effectively a MCH Foe's Requiem).

Come on SE, there's a LOT more you can do with MCH than some convoluted heat management system.