The fact that spells are a finite resource makes this whole conversation kinda silly. Sure, a wizard can be a reasonable facsimile of a rogue in a part-time capacity, at the cost of doing what he's actually good at. Or maybe he should just stick to doing what he's good at? Crazy talk, I know. If that wizard was in my party, I'd be all over that silliness - dude, stop farting around opening doors with your mind and get out the friggin lock picks. Don't come crying to me when you take a ogre club in the face because you ran out of juice to cast shield. Sheesh. The next time we're back in town I'm hiring a Hobbit, I swear to Tymora.