Okay I have two main suggestions for character classes.
Ever play as a gunner and your in a match where you survive long enough to run out of ammo?... Well I have done that quite a few times. Sure you could charge the enemy and go down in a blaze of glory and a body full of holes with nothing but the trusty ole .45 in hand. Or you could call up your brave little assistant gunner/ammo carrier.
These hardcore little lads would carry an extra 400 rounds/two boxes of machine gun ammo. Just for you. You probably won't last long enough to dump those. But still! It would be nice to have an ammo bearer at your beck and call.
Ever been in a heavy firefight stuck in a rut and pinned down like a donkey's tail at a 6 year old's birthday party? Well... I know I have. Sure you could play it ww2 ruskie sniper style and poke your head out to reveal their position to your friends elsewhere. Or you could tell your Fire Support Operator to call down hell's fury on the enemy position!
Strap em with a 16 and a handful of frags, flashes, and smokes and a radio pack with a connection to god's lightning bolts. Put in a request for heavy metal and wait for the dust to settle. Oh lookie I'm not pinned down anymore!
Oh and those Ghuille suits from DF2.... bring those back for all us hardcore snipers out there.
Thank you have a nice day.