There are allot of games who have this approach. Most roguelikes, all elder scrolls games and plenty of rpgs (or games with rpg elements) use this.
in morrowind, I do believe you couldn't join all 3 of the houses

.
Trolololol.
But I do like the idea, of maybe, loner trait giving another (1) tag skill.
+10% experience is complete crap, though, I suppose if you're just some 1 ch build and all it might seem nice, but still.
And of course, to balance it you'd have to take off the +10% exp.