I more or less agree with ALurker here.
There is some ambiguity in what makes a good stunt, but not an infinite amount. So trying to sort out the dreck isn't worthless.
It's not possible to follow the rules legalistically, because as ways and means says they're more like guidelines.
I'm trying to avoid getting rid of stunts completely, since that has the anti-inspirational effects mentioned by Silverblaze. I'd rather add restrictions or reduce bonuses.
Tsunami's proposed rewrite of Do You...etc looks pretty good mechanically, but I do kinda doubt the flavour. Making your own knife wouldn't let you fight with it if you have no skill at knife fighting, would it?
Unless the knife was special somehow...I think that maybe this can be made to work.
But I've grown attached to the modifying version, so I don't think I'll get rid of it even if we come up with a new version.
Anyway, the solution proposed by The Mighty Buzzard for the supernatural-ness problem doesn't help. Pure Mortals had no reason to take the stunts I'm thinking of anyway. And there are mechanical differences between stunts and powers that make mixing them up a poor idea in my opinion.
Ideally, Pure Mortals would be able to take any stunt. But some of those stunts would be pointless, since they'd expand capabilities that a mortal doesn't have.
The problem is more or less just flavour. Some of the stunts don't feel like stunts.