Well I suggest:
Something like Recruit, Frontsoldier, Battlehardened and Veteran etc.. May give them bonuses like the suppression effect (higher the lower it is, also when someone is hit near you), sounds like RO but it would be a "goodie" with sense. But keep fingers away from "unlocks" :laugh:
Also it could be interesting to add somekind of speeches of the "rank", something motivating, insulting or for recruits they say something depressing.
Please give the MGs or Support Weapons fair status, like when its placed correctly it will do devastating damage to troops... its somewhat i missed in RO2 since maps are too small and riflemen can zoom like a sniper.
Also what would be very important to me personally and maybe for some other guys:
Capture points, maybe you could do this in the Darkest Hour scheme, it was very fun and target/goal optimized to reach the cap zones. the main thing is to cap the zones in a chronologue way and lock the zones behind the targeted zone to prevent guys hangin behind the front