Most of these suggested changes are too complex, I think.
Best left to 5.0, IMO.

Adding dots (to cooldown, wildfire, flamethrower etc) is not a good idea. MCH is not a dot class, and most classes got their dot removed to clean up the rotation. IF you add a dot, you have to add a meaningful reason to have the dot.

The problem is that, while there is a mathematical answer to overheating, the answer is not obvious, and a studious MCH can look and not find a clear and concise answer.
If the overheat bonus was, say, 20%, the answer would be clear - and I think that's better for the class overall.
The trick, I think, are small easy to make changes that don't overhaul the class, but bring it to where it needs to be.

Right now it's the least played class by a long shot, and I think more people would play if the rotation itself gave you a NICE BIG HINT as to what to do to play best.