We can agree, machinist in the current state are bad in hi-end duties like ultimates and its not his dmg but lack of utility.

Dancer and Bard have party buffs, heal, regen and shield, also can increase healing or even "esuna" on one target, and they still do more dmg than machinist.

So I think about that for a long time and have 3 small ideas on how to fix the machinist with no giving him raw potency increase.

1) new skill: Bishop turret -> MCH put down on ground small turret and taht turret generate small 5 yalm shield giving 10% mitigation and 100 regen for next 15 seconds (almost like Collective Unconscious form AST)
2) Flamethrower -> now give Heat Gauge - full duration give 50 heat
3) Barrel Stabilizer -> now give additional Battery Gauge 50

Let me explain number 2 and 3 -> now in the new ultimate you have limited time to burst down then boss are untargetable, only Machinist have problems with that because his Gauge fills too long. In down time mch can't build a Gauge and basically do nothing. Flamethrower with heat increase will fill time where boss are untargetable and you need to build Gauge and also Barrel Stabilizer gives you 100% option to use queen when you need it.