Personally, I see no use in overcomplicating the system... Missiles need something to balance them out without nerfing their capabilities into oblivion, so make them take warheads, since, you know, missiles need warheads to blow up. Every other weapon type doesn't seem to be too OP, and we already have an Effects system, so I see no sense in complicating things with having types and tiers of ammo for everything unless you guys want to replace the slave/effect system outright, with some kind of dynamic ammo system, which would be more complicated and a lot less fun, IMO... So as I see it, just don't mess with them for the time being, there are better uses for the devs' (and players' - that would be a lot of refitting!) time.