Having Played MCH at 70 more and done some dungeons alot...and having spent a lot of time on the level 70 dummies...here's my thoughts on what I'd like to personally see changed:

1.) I'd like to see something done with flamethrower. It seems like it was a decision made because it sounded cool but didn't 100% mesh with the job, but they needed to have -something- else other than barrel stabilizer, and somehow this was just the best thought put forward, but not really the -right- thought(solution)

2.) Gauss barrel should be available at a much lower level, like level 30. At level 30, it should provide 5% dmg increase to all actions, with a trait at level 64 to increase it to 10% while between 50 and 100 heat. This solves the lack of proper development planning for using the job at lower level dungeons(a), rewards good MCH with dps increase maintaining 50-99 heat(b), and the 10% should carry through into overheat, so we also get the overheat % increase to make it more worth-while(c). This also boosts wildfires so they should hopefully be closer to Sam's omgwtfbbqslice' slash move.

3.) Cooldown should be available at 30, removing 10 heat or 15 heat. At 62 a job trait should increase the amount of heat to 25 like it is now. This maintains the current design, but fixes the failed planning to address the job's functionality at lower levels.