Stormraven - I'd definitely be treating a consequence taken in this form as a normal consequence with all the bad news that implies, yeah: say I did take a severe consequence for 6 focus slots, that's it, there goes my slot for -6 stress, and I have a bad physical injury that's subject to compels and everything.
But are you saying then that you wouldn't charge refresh/fate points for this? Because that would be why I would put them in, as limiters against the possible overkill you're saying can happen. I mean, this guy is a wizard; he's not going to have a lot of refresh XD.
Haru - I feel that it needs a stunt because part of the intended effect is that this removes the need for my character to carry physical focus/enchanted items? I mean, I can't be compelled into "oh, you forgot to bring your blasting rod", I appear unarmed everywhere I go (while Harry Dresden points out that bringing his staff is effectively open carry as far as supernatural beings are concerned), I can't be disarmed (unless I'm literally dis-armed)....
And I want to tie it to consequences rather than Endurance simply because I feel like the character causing himself injury like this should have consequences (pun intended). Like, I mean, taking a knife to your own flesh over and over again really shouldn't be dismissed as flavour.