As I recall, Cooldown (above 50 heat) is equal to a Heated Slug Shot, so it's hardly a loss to "never use", plus in those rare occasions where you don't want to push for or need to withhold an Overheat but you're already near 90/95, that's when it still does its job as intended.

People were avoiding Overheating back then because doing so proved to be more of a loss overall than the 10% gain it gave. Buffing it and making things line up a bit more nicely made it clear that you were supposed to build and spend, not unlike some of the other jobs and their gauge mechanics, only most others don't have a forced trigger, thus you still have to plan ahead. And with proper planning, MCH has a smooth, clockwork-like rotation that still gets the job done, and done well.

I'm with the other person that said it: MCH doesn't need a massive overhaul (and we're quickly reaching the point that IF they keep screwing with it, it's only going to drive people away from playing it for lack of stability). Give it a few QoLs and it'll be just fine.