1. close combat/ assault (shotgun/smg, extra toughness)
Butcher, Rumbler, Brawler, Psycho?
2. rifleman (assault rifles/carbines, mid range soldier)
Grunt, Jarhead, Trooper?
3. marksman (sniper rifles, battle rifles (like garand, m14), low toughness, extra aim)
Deadeye, Sharpshooter, Assassin, Hitman ... or more randomly Potshot, Skinny?
4. Support gunner (LMG, launchers, can carry more equipment)
Heavy, Tough, Meatshield, Brute, Bruiser?
5. Medic (smg, can heal good, low toughness)
Doc, Sawbones, Stitches/Patch?
Also you may want to look at the Jagged Alliance games if you haven't.