Of course this also contradicts game mechanics. For instance, if you charm someone and open up the persuasion wheel you will observe the effect was almost instant. And what your saying is that persuading a person like "The hot chick in tight cut off clothing, with a nice smile, sweet voice and charming manner." would take a long time to to persuade someone to 100 disposition. Charm and Command Humanoid/Creature is supposed to against their own will. It's not like they heard your voice inside their head when their disposition is 0 and immediately fight to the death for you. How about calm? Do you just nicely ask the minotaur to stay put while he's trying to viciously impale a horn in your freaking face? It's supposed to be a skill where you make people do actions against their will.
Ah game mechanics.. we have a game that takes anywhere up to twenty hits from an over sized war hammer to kill a bandit.
Yes the spell is instant, but what is stoping everyone else suddenly noticing the sudden change in behaviour?
Think of hypnotisim it's not a battle of wills, it's a way of persuading someone to do something.
No matter how willful you are they won't do something they're opposed to without a good reason, someone that is good looking or has a way with words and personality is better for this.
Minotaurs are beasts, intelligent somewhat, you note some can make animals behave better not with willpower but through behavioural science and studies of personality shifts.
Spells also require words in fantasy, they require songs, words of power, gestures of the hands / body, ingredients all of these are not in CRPG's as it'll be a nightmare to do so.
So again game mechanics contradict roleplaying mechanics, and fantasy mechanics.
Also you've gone from intelligence to willpower, you could say strength as to throw balls of energy requires might.
Endurance to harness that raw power.
Luck as it requires it not to get fried.
Agility as you have to get close and touch someone, or hit with a ranged spell.
Speed to get through the mental defenses that a target could erect before you cast a spell.