While i personally think it’s a bit silly to just disregard potential options due to “principle” (i agree with Wigwam that it looks like that), i will say that the entire appointee spiel isn’t a great solution either.
The reality is, there’s no “apointee” for Motability. You have to go to the DWP and appoint the apointee. It’s not just “picking up the car” that comes with it, but also actual legal responsibility for the contract, as well as the fact that his pension/PIP/other payments get paid directly to the appointee. It’s akin to a legal guardian.
I can understand why one would be hesitant to appoint one (and in fact, i could understand someone being hesitant to agree to sign a contract on his behalf with MB considering that they’re the party held liable).
The other option is a Nominee. Now, i don’t know if MB would let a Nominee (and yes, there’s a huge difference between Nominee and Appointee) pick up a car, but it certainly would be worth asking them. If they allow it, that Nominee (can be anyone, be it family, neighbour or buddy) could be added as a driver temporarily (MB has the option for that, iirc 30 days) to pick up the car.
To cancel the order over what looks like a principal issue, i don’t know. To me it seems like shooting yourself in the foot (cancelling the order) just to make a point really isn’t that sensible, considering nothing will change, at all, whatsoever. The only thing different would be that you’re out of a car.
Prior: SEAT Ateca Xcellence Lux 1.5 TSI DSG MY19, VW Golf GTE PHEV DSG MY23
Current: Hyundai Ioniq 6 Ultimate
Next: we'll see what's available in 2028.