I find that the gunner class is very niche and that there are not many opportunities to make this class as useful as the others. My biggest problem with this class is its lack of flexibility : outside of bipoded fire and extreme CQB, this class is almost worthless.
What i would suggest to fix this is to reduce the recoil of the LMGs to make them somewhat decent at normal combat, while still punishing mobile playstyles.
If you think this is not a good option, I would give the possibility to gunners to have access to normal assault rifles and give them access to Drum mags and bipods for reduced costs.
If you still think it is not a good idea, I would suggest adding weapons like the MG36 or the RPK (which is already in the game files if I remember well) who could bridge the gap between LMGs and ARs : worse than ARs for mobile fire, but still better than the current LMGs, and better suppression potential than the ARs, but still less than LMGs. It would be easy to balance this since current LMGs have a great potential for suppression : great damage and penetration for the PKM, and huge volume of fire for the M249.
What do you think about this?