Yeah, permanently cursing my own wand arm off is not my first choice, though certainly given the choice he'd take no nose over no wand arm.

Rachel Brodie said she'd cruciate me if I really wanted to give it a go, but I didn't take her up on it. Anyway, I think it would take quite a bit of cruciatus to convince him I'm not worth taking over. Enough that possibly I'd rather lose an arm.