This has been up here a couple of times, twice by me. But rather the focus was more on just directing the attack. That would seem more a plausible idea versus controlling what spell the minion casts.
So far I've yet to find a wizard against the idea though.
This would help fix the issue of a minion casting a good spell on a bad target:
Giving a myth blade to a fire wizard, giving pips to himself which does nothing, etc.
I think they should put the right click to discard option on the spell your minion has selected, and if say its an attack ..and you dont want him to mess your traps up you just right click to disguard his spell, the minion will then choose a new spell based on the fact the player discarded his attack and would cast any non attack card they had or pass if they had none. This might be easyer to incorperate than adding total minion control.
I think we should have a page in our book about controlling our minions. I have a life minion and a death minion. All the minions that heal should have an option like heal the person who needs it the most. They should also be able to level up according to how many fights they're in. I would love to put an amulet and pet on them also. They should also get the cards we get.