Something i had written for flamethrower from an older thread.
Famethrower should build heat, It should also allow movement, albeit slowed as well as be manually aimed. I don't see how shooting flames out of your gun wouldn't build heat, and standing still while you flail around just feels like an arbitrary restriction. I think flamethrower would have a particularly good spot as an AoE opener to quickly build heat to transition into crossbow, and also as a damage boost when used with overheat on. (make it blue high-pressure flames) - This could only be used after the initial pull as flamethrower would still be on cooldown obviously.