Now i will try to offer some solutions that would, in my opinion, solve the problems while keeping current design. Because i know that many people are afraid of next reworks since it can be turned to something worse.

1. Both original and heated main combo actions are relics that should be already gone. We need set of new well made animations with satisfying gunshots.
Main combo won't be related to Heat Gauge.

2. Crossbow is now trait replacing Spread Shot. Flamethrower is new AoE action during Heat Redirection (look below for explanation).

3. Adjustments to Hypercharge. Action renamed to Heat Redirection. Adds X stacks of Heat Blast and Flamethrower (shared stacks). While stacks are active Gauss Round is changed to Heated Gauss Round.
Flamethrower no longer locks you in place. Shorter duration of one attack, similar to Crossbow. Flamethrower is now Multitool action.

I would say for the sake of proper animation flow animations for Heat Blast (aka Heat Dab) and Gauss Round should be adjusted, it looks pretty weird at the moment. I would also suggest removing Gauss Round and replacing it with something else, its a relic of Gauss Barrel which is already gone.

4. Battery Gauge removed. Hot Shot is now DoT (to be discussed). Turret and Automaton are two separate summons with their own cooldown. Summon ability changes to Overdrive while machine is summoned to avoid ability bloat.

5. For the sake of Gunner part of the job Reload should return, even if it has some simple design like "Increased damage for next X actions".

This is everything i wanted to say, i tried to describe it in points so you can easily point out which ideas you like, and which you don't. From my point of view it would really improve how the job feels like and fix lore issues.