Since the main benefit of the staff is as a defensive bonus - I don't see like as effective when only used in one hand.
I would allow it to be used as an implement in one hand but to gain the implement effect I would require both hands (or do we want Wizards with a light shield in one hand and a staff in the other).
But then why would you not allow any PC to carry a staff in two hands and get a defensive bonus from it?
The bonus is not combative in nature, otherwise, anyone could do it.
It's magical in nature. Even another Wizard cannot gain that bonus if he is not able to use the Staff implement. Think of it as a mini invisible force field that Staff Wizards can put up.
And yes, if a Staff Wizard takes Str 13 and the Light Shield feat, I would allow him to have +2 to AC. Why not? He paid for it and gave up something else to acquire it.
Last edited: