My Field Medic loadout for the MAS server is currently sitting at:
Gauze Gun (modified Medpack to make it damage enemy teams and heal allies, lessened healing slightly)
Nailgun (essentially SMG)
Crowbar (Melee)
Tranqulizer R (special weapon)
Depending on how self-tanky you want your medics you can give them the Syringe, but the general gist is you want your players to actively HEAL thier buddies, and not just syringe themselves with ALL the drugs and tank the game to hell. As a result, Gauze Gun and/or Syringe combined with a SMG/Machine Pistol/Duel Pistol works moderately well, as they got a fallback weapon that way.