Well obviously you don't need 'skill guy' to do skills, any more than you need 'fighter guy' to do fighting or for that matter 'spell guy' to do spells. It's not like fighters have no skill points or NWP's. There is no reason why 'spell guy' should be completely inable to fight or be totally lacking in skill. He's just relatively lacking in fighting ability and practical skills compared to some others. The point is that being particularly skillful and knowledgable outside of combat is a different area of class specialization than being skilled in combat.
I worry about this approach. It's starting to sound like "class niche exists because class niche can exist". What does it represent?
To imagine a simple system
Fighter guy is good at combat and brawny things.
Spell guy is good with spells and academic things.
Skillful guy is good at academic things, brawny things, and practical things.
So indulge me on theming this: Which character from the game's literary foundation is a Skillful guy?