It would appear that the online servers for the game are back down and potentially for good. No one has unlocked any of them (online) since September. Not sure how long you like to wait until flagging them as but there are 14 total that are now discontinued/unobtainable by legit means including, in no particular order, the following:
Soldier of Misfortune
Mercenary
Warlord
Field Hospital
Professional
Upgraded Player
Hired Gun
Superior Captain
Battle Hardened
First Response Team
Safari Tour
Best In Class
War Party
Adventurer