OO can always get the account back after a name change. A name change is only really useful in a couple of situations.
1) Transferring the characters onto your main account
2) Making people believe it's yours through Real ID
Now, here's what I'd recommend doing.
Buy a new Battle Chest (preferably in-store) + MoP - let's call that WoW2, and add it to the existing Battle.net account. This way you'll have CD keys.
Now transfer the "main" character from the original WoW1 account to the WoW2 account, along with any other characters you want.
Once that's done, create a new Battle.net account with the same first and last name, different SQA.
Now log onto the original Battle.net account, and ask Blizzard to transfer the new WoW2 to the newly created Battle.net account, because you decided to keep the accounts separate. Answer a few questions like SQA, possibly CD Keys. Now you have the WoW2 on your new BNet account, complete with all mounts and characters you want. Because OO doesn't have CD Keys, it's impossible for him to recall the account. Recalling characters may be possible.
Bonus points: Email
[email protected] from the original Battle.net's email address, and ask them to remove all personal information relating to this account. Answer any questions they have. Now the original account will be irrecoverable by the OO.