Any additional ammo you add to the game can still be taken by engineers adding more does not change that fact, while engineers can still perform the other Repair/Buff tasks that gunners cannot do effectively.
A lot of this too.
New ammo types that damage the gun/ship only promote engineers because, especially with heavy disable right now, gun damage is a problem best solved by engineers.
For an ammo type to actually promote gunners, it would need to be inherently productive for your ship and your team, but would need to not be inherently powerful.
New ammos don't need to deal massive damage. The guns themselves already deal good damage, and your engineer is going to take those ammos that complement this.
New ammos need to reduce the damage of the weapon and provide other opportunities to benefit your ship and team.
Consider, you would (probably) not make your engineer take an ammo that will reduce your damage output since that will be their only option. However, a gunner can still take the damage ammos
along with the niche ammo types that actually reduce your damage output.
The strength of the gunner is their versatility and ability to be useful at different ranges and in different situations. Right now the ammo types focus mostly around your damage output and range capabilities, with the exception of heatsink. I think new ammo types need to be types that you would not want your engineer to take in any situation. Types that are inherently not good if your choices are that ammo and normal. But they should be capable of being used very effectively if you have a gunner who can load that ammo in for a single clip to provide you with some form of advantage before switching back to more conventional ammo types.
Examples I've seen in this thread being Anti-gravity rounds, tracer rounds, and my own impact ammo.
Anti-grav would allow shots to fall upwards instead of down, making mortar crazy interesting, but not an ammo you would take with your engineer since there are better ammo types for a player who is limited to normal +1.
Tracer rounds would have to deal next-to-no damage while giving a percent chance to "spot" a ship if that ship is hit. Engineers taking it would sacrifice their damage output, but a gunner would still have 2 other ammos to take damage ammo types.
Impact ammo would allow each gun to deliver impact damage instead of its normal damage type. The damage would be severely reduced to where an engineer with a mallet could maintain anything being focused, but the impact would be distinct and noticeable. Engineers would again be weakened by taking it, but a gunner could easily fit it in for interesting situations/tactics.
Another idea that is probably infeasible and may not be desired would be healer rounds, which deal 0 damage to enemies, and 50% damage as a repair to friendlies. A close range ship could then support a long range ally by assisting with repairs while the long range ally snipes. But your gungineer taking this would immediately nerf your ability to fight, making it mostly only desirable for gunners.
In essence, if ammo types are the immediate band-aid to the problem, then we need to come up with ammo types that a pilot would love to have available on their ship, but that would not be beneficial as a singular ammo for a player.
TL;DR: Think of ammo types focused around utility, not damage - damage ammos will be taken by engineers, while utility ammos are taken by gunners.
