Just an idea i had. When you start a game the game picks out one random class from maybe 3 branches of skills: medical, technical and physical. For example you'd have basic first aid, doctor, surgeon for medical skills. The chance of being basic first aid class would be comparatively high compared to surgeon class which would be rare. For other classes there'd be tinkerer, mechanic, engineer, brawler, melee fighter, rifleman, sniper, small arms ect. This would help stop people killing each other on sight as you'd need other peoples skills in order to survive and you'd never know what skill they had unless you asked. It would make sence too because people would have their own skills learned from their lives prior to the zombie apocalypse. At the moment people kill because everyone is the same which makes life cheap. This game has to emphasize the unique qualitys of every individual charactor to give them any worth and consequently avoid having their heads blown off for waving hello.