As it stands right now, there's no way to rebind the controls used by the spectator camera (as far as I know, correct me if I'm wrong). This is a problem for users with keyboards that lack a numpad (laptops and such), as some of the keys used in the spectator view are only bound to numpad keys.

Right now, the spectator system is really the only commonly used feature that lacks the ability to rebind keys, and hopefully it's not an feature that's too difficult to implement.