I don't see why an Orb of Imposition has to be an orb. An orb would function the same if it were in the shape of a staff
I recently build a controller wizard, and I'm tempted just to decree that he has affixed his orb to the top of his quarterstaff.
Exactly. I don't like the visual of holding an orb. I do like the visual of holding a staff. I certainly don't see a problem with fluffing it up with staff that has a socket for an orb at the top for my character.
Mechanically, rule that using your "StaffOrb" as an Orb requires a different grip than using it as a Staff. It takes a Minor Action to change your grip.
This is *identical* to using a Minor Action to draw a new weapon.
You have not changed any rules. It's 100% fluff. Even the Second Implement feat stays balanced.
The only problem will be with "found" staves -- they may or may not have sockets for orbs (most likely, not). The wizard will need to craft his own staff most of the time.
You can go even further and say that the same thing works with holy symbols and shields: the shield has a slot to clip in your holy symbol. You still need to burn a Minor action to swap from "Shield" to "Implement", and during that time you lose the defense bonus of your shield. I'd also make "Lesser Pact Blades" or "Lesser Holy Avengers" that need to be enchanted twice (once for the melee part and once for the implement part) and require a Minor action to change modes (effectively two daggers glued together). Etc, etc, etc...
None of this changes any rule, it simply uses fluff to change the visuals.