That's an excellent way to classify the different skills. Would that be how it looks in-game during character generation?
Indeed. I would imagine class creation to have a base menu where you can name it, create a description, pick your main specializations (from each of the categories besides legendary. Combat, Magic, Stealth for adventurer. Crafting, Work (for lack of a better term. For stuff like cooking, fishing, etc), Fitnes, for Citizen. Warfare, Speech (again, for lack of a better term), etc for State.) and you could then select your class skills, which would be central skill, majors, minors, misc. Which could all be mixed and matched as you see fit. Your attribute bonuses would be generated according to the skills you took.
For example, lets create a male Nord Knight using numbers from Morrowind as a base. (Some skills are just made up on the spot)
Nord
Agility 30
Intelligence 30
Endurance 50
Luck 50 (I bumped it to 50 because balance should dictate that I think unless you pick a birthsign that says otherwise)
Personality 30
Strength 50
Speed 40
Willpower 40
Specializations:
Combat
Work
Warfare
Central Skill: Longsword
Majors:
Heavy Armor
Heavy Shield
Athletics
Tactics
Horse Riding
Minors
Restoration
Enchanting
Speechcraft
Mercantile
Smithing
So with that class picked and a birthsign of the Lady (Personalty +25, Endurance +25), we would end up with the following stats (note that these are just mostly just arbitrary numbers. The real thing would have a real formula that would do it properly):
Health 150
Magicka 75
Stamina 200
Strength 75
Endurance 75
Speed 45
Intelligence 40
Willpower 45
Personality 65
Agility 30
Luck 50
Combat Level: 8
From here you could also pick character traits such as favored gods, political alignments, etc. Or leave these options blank and let them grow over time
Now obviously those numbers seem rather high for something claiming to be balanced (even despite the fact that I made those numbers up) and the automatically assigned character level, but this system would be coupled with my solution of combining GCD-like leveling with a removal of caps, so in truth it wouldn't be unbalanced at all, and with proper scaling where appropriate most of the world would adjust to your characters beginning level.
This class system wouldn't be permanent however, as there would be not only be an option to deny a class altogether (where your combat level, attributes, etc would be derived from all skills. This option would be slower to level than a by using a class, but would give complete control over how you level (for those that like that) and would eventually come out to an even end-game regardless if the same sorts of characters were created, just sans class. Perhaps this option could result in more power. Or not.) but also the option to freely change a class (with penalties to xp rates for a short time, and cost in gold) or abandon one at any time.
And of course to make this even further viable as a system, one would need to see attributes fleshed out more so that they influence the world and in order to encourage class use NPC responses would have to be overhauled to respond to character traits if only in a subtle way that would be beneficial and balanced. Increased and/or decreased dispositions would be basic (and as such, increased or decreased rewards), Hostility a bit more complex, Worldly events (like visits or visions from the gods, assassin or mercenary attacks with greater reason behind them, etc etc) in the advanced.
In fact doing this makes me want to make a new topic just for it.