Should be a pretty easy one for the Demons to defend in all honestly. AFL uses an adapted version of the Glasgow Concussion scale, they'll simply need to snow his rating under the scale that proved he hadn't fully healed to full health and they've successfully done their due-diligence.
Wouldn't put it past Lumumba though to suggest "interference" or negligence in the doctor's assessment which would take the case in an entirely different direction but I surely hope that he wouldn't consider potentially ruining a doctor's career for the sake of some $$$$- and headlines.
Not only would he do that in a heartbeat, but he'd do it with the genuine belief that he's been wronged, because he is completely delusional and doesn't have a grasp on reality.