valid Asthetic,visual ideas.

[Vanizzzero 3]

Make tanks emit smoke from multiple places around tank each time you loose Health.

Add effects and knock backs to turrets. Example(Smoky, Railgun, Magnum has effect of their barrels to go back a little bit after shooting). So add this feature to Hammer, Twins, Thunder, Shaft, Gauss.  

Firebird: When holding "fire" the turrets barrel starts glowing from the heat, then when you stop firing the barrel cools down(refills ammunitions, recharges).

Freeze: When holding "fire" the turrets barrel tip turns white a little and with each time you fire, more of the turrets barrel turns white from coldness. But the whiteness will not go off until player dies, it just stacks up.  And when player respawns whole process resets. 

Vulcan: When holding "fire" the turrets barrel starts glowing from the heat, then when you stop firing the barrel cools down(refills ammunitions, recharges).

Ricochet: After every shot the turrets barrel tip splashes the same color as the shot particles are. After dying the whole process resets.

Twins: After every shot the turrets barrel tip splashes the same color as the shot particles are. After dying the whole process resets.

 

[Iron_Man 2,376]

Valid

I've removed the first part of your idea regarding bringing back of different skins for different modifications. It is already planned but for distinct future.