Ammo weapons in general - not so much that they aren't effective, just that they are rarely worth using unless you are fighting through systems where your ammo is in ready supply (ie, Ranx gunships

) and doesn't weigh 20 tons (ie, Ranx dreadnaughts...

). Having more enemies that would dependably drop the more popular missiles would help.
On the other hand, if more of the ammo based weapons had effects that made them useful as support weapons I think they'd be a good bit more useful, particularly with the flexibility that launchers allow.
If they had larger area effects that deliver shield or system disruption, engine disruption, weapon disruption, EMP, knock-back, spin, gravity traps and so on - so that you weren't using them as primary DPS dealers, I could see using them more often. Your ammo would stretch a lot further delivering effects rather than DPS.
As it is, using missiles for DPS delivery seems to pretty much empty your ammo stock in no time at all - at which point I just don't even slot the launcher and revert back to my default beams and howitzers.