Multiplayer mechanics

The game could use better functionality to make multiplayer mechanics more interesting and variable. Classic roles like heal, tank, crowd-control/interference and damage could be employed with a few tweaks.
Health bars for each player could show a healer class who to use medical ammo on next.
Shields, flares and boomboxes/radios could help a tank soak up damage and keep attention on himself.
Crowd control is already there with shock ammo and fireworks (if you could only remove the anti-gravity effect that comes with it).
Damage is also already there with sniper rifles and grenade launchers.