Just a point that people might not have realised:
Apart from the rogue (who requires a specific type of weapon in order to use his powers), every class can in fact make use of their abilities while unarmed and bound to the point of being under the restrained condition. Fighters, rangers, warlocks, mages, clerics, warlords can all use their powers either without any implement, or by substituting an unarmed blow.
Further, I'd suggest that for the sake of not having bizarre arguments about how exactly one can become immune to magic (a bag over the head blocking line of effect opens up a lot of odd doors), being blind probably is a better condition to apply.
That means that, with the exception of teleportation, the wizard is in exactly the same boat as any other character when captured.
Teleportation unfortunately means that all precautions become for naught.
Might I therefore suggest that the rules text which says that teleportation trumps physical restraints (ie - breaks immobilisation effects) should be excised? That makes everything fair and simple - the wizard (or warlock) can still teleport 10 squares, but he teleports and remains bound, gagged and blindfolded, and can be easily recaptured, the same as any other character who might, say, successfully get an unarmed stun off and run for a short distance.