Brock can wear the strap. The Rock is wearing it now. WWE would make it work. Maybe have Brock leave with the title like Punk did. It's not out of the realm on impossibility, for Brock being able to hold the strap for certain amount of time.
He's lost at the last 2 WM's so he's due a big win. Having Lesnar feud with the NAO though would be a major comedown, they're hardly at the level Lesnar pictures himself at. Not when there is Ryback, Henry, Show, Orton, etc to feed to him.