Q: What's the role of intelligence, charisma and will in game? Why isn't there any thief, doctor, ranger or scientist skills?

A: Yes, we don't have scientific of magician's skills, 'cause our characters will be mostly kinda soldiers. But they still need intelligence, charisma etc. These stats have their own roles in the game. For instance, strong will helps you not to get accustomed to some of the chemicals, helps to survive when you're heavily injured.