Gantrakk

I would probably call the heavy plus sniper "support" as it is reasonably descriptive of their roles and shouldn't be able to be confused with anything I can think of. A suggestion for the LMG if you find you use up a lot of ammunition, give one ammo box to each of your other soldiers to drop next to him when he needs it. A similar distribution of ammunition can be used for rockets to get a good supply without overburdening one man, after all if they want their fire support they can damn well carry the ammo.