MCH Overheat should activate automatically

[CKNovel]

I don't see why we'd want to spend a button just for that, though? If it had a big bursty hit to start things off and we could later reuse it for a less efficient but burstier use of stacks, sure, but otherwise we may as well leave it on the same key.

Think of it as Gnashing Fang that starts the cartridge combo.
Instead of being Gnashing Fang -> Savage Claw -> Wicked Talon, it would be:
Heatburst -> Heatblast -> Heatblast -> Heatblast -> Heatblast.

All of it on the same button. Yes, that's mainly fluff.
In my opinion, the best of world would have an Overheat starter -> Heatblast*3 -> Overheat Finisher.