What do you really need to relearn in an AOW? Everything? Probably not. Do you need an actual cert? Probably not. I recommend that most people simply go to the next level and do an AOW with an instructor with FULL disclosure upfront.
I agree most people wouldnt need to redo the AOW skills, except navigation and use of lift bag/ SMB. I do alot of wreck and drift dives were navigation to get from one wreck to a second is good, or when reef ends head 100 feet to the east/ west etc to hit a second ledge.
taking an aow class should include a review of OW skills if needed.