How about removing normal ammo or allow people to have 2 active at the same time ?
There is only one helmet, and its a good thing to bring a dedicated pilot with pilotingtools.
With just one of them you are screwed in many situations where you need one of the others.
There is only one baloon/hull that is damaged/broken/burning and its a good thing to bring a dedicated engineer.
With just one repair tool you are screwed in many situations where you need one of the others.
There are 3-6 Guns on your ship and a fat chance that the right gun for every range/damagetype is ready to fire.
They do perfectly fine with normal ammo.And the other ammo's purpose is to squeeze out up to 10% more damage or
make them opperate out of their comfort zone (reduced arming distance,reduced weapons spread,less projectile drop )
because the proper gun for that situation was broken (+1 engi) or on fire (+1 engi) or already taken by another player.
With just one ammo type you ..... will have to use the normal ammo for half the guns on the ship? or run between guns to be flexible?
Add the fakt that chem spray (+1 engi) and the buffhammer (+1 engi) stack with ammo buffs ,
but different ammotypes that fill a similar role don't stack with each other;
and it gets hard to see a justification for a dedicated Gunner.
Half the things his addidional ammo does can be done better by additional engineer tools, and the rest has marginal or very situational impact.
But with 2 ammotypes stacking I can see them on eye level with the engineer tools and a whole new level of flexibility/more ship loadouts that need an gunner.
It will require some fine tuning , but each ammo already comes with a drawback that works as a adjusting screw to give them the edge without making them overpowered.