It may not be exactly 'save or die' but creating compels that specifically shut down that one thing you use Wizards for (who as a consequence don't have a lot of fate points to avoid compels to begin with) and causing stress on the same track they cast spells as a 'happy side effect' is pretty suspect. And you want to use your fist skill, from what I'm gathering? Presumeably so they have to use athletics to defend, which isn't going to be as tough as Disc (their stat for mental defenses). It's hard not to feel that's a bit overpowered.
What about "blinding" a wizard? Now he can't target anyone with his spells. I suppose he could still do full zone effects, but he might hit his allies. There are lots of nasty compels that go along with blinding, such as dodging mediocre. IMO, a blindness aspect is closer to a save or die than anything else I can think of...and I'm sure people can think of lots. Where's Belial666, I'm sure he could come up with half a dozen awful things to do to a wizard.
What about "stunned"? Now you could compel that to say the wizard is unable to act
at all.
I'm sure given all the people on this board, we can think of some really nasty maneuvers that could be compelled that are harsher than having the wizard cast at a lower power of having them spend a few rounds trying to remove an aspect.
Remember, compels are
negotiated.
EDIT
Sorry, Thrakkesh, I misread your post...I thought you were talking about maneuvers.
No, if
I were to allow a Chi Blocking Channelling attack, I'd have the wizard save with ... probably discipline...
If it were a magical beast that channels via a different means, I'd allow them to use whatever skill it is they use to Control their magic. So basically, the caster would, most likely, get to use their highest skill.
How I see it, the fists attack isn't doing the actual damage, it's the energy that the fist attack is channeling that is doing it - so that's the more important thing to save against.
But that's just how i'd do it.