I'm coming from the idea of not competing with BRD for buffs, but instead becoming the ranged debuffer of the team. Also I wouldn't want ALL of these added to MCH just 2 or 3 of them. Im spit balling ideas that wouldn't include more buttons or changing how the class plays (too much.)

1) Add a vulnerability down debuff to our 1-2-3 combo .. 1-2%, and it can be maintained by doing this combo. Let the debuff fall off in 5-10s

2) Give us our old DoT shot back. Or add a lingering DoT effect to flamethrower so it can spread DoTs around and get a little extra on the bosses.

3) Up the duration of dismantle.

4) Add a bind or stun to the knockback shot.

5) One of our turrets could have a vulnerability down debuff attached to it.

6) One of our turrets could slap on a slow debuff, or damage down debuff, or a silence debuff.

7) Rapid fire could spread a critdown debuff, or blind.

8) (My only party buff idea) Turn cool down into a party haste instead of an attack (spreading the heat to make everyone quicker, because magiteck reasons.)