I always liked that AD&D system myself; EinTroll also mentioned this earlier. Definitely some things there Larian could work with.
So as I understand you, there would be three main variables affecting skills:
1) Player level = number of skills learnable at one time for all skill categories (currently, the individual "skills" abilities control this)
2) "Skill" ability level = effectiveness of skills in that category (damage, AP cost, cooldown, etc.)
3) Controlling stat (STR/DEX/INT) = maximum "level" of skill learnable for skill category(ies) related to that stat
Am I getting you?
I have to say that I love this idea. I think it's way better than the current skill system.