Transfering from the current car on the scheme to a new one should not be a big issue, When it was first put on they would of looked at, if it was relevant to the leasee or not.
I did have an issue putting mine on the current car (my 4th on the scheme) as it had been on retention for a while since i joined the scheme and the time was expiring and i’d lose the plate, as you can only keep it off a car for 10 years now, were prior to that you could pay a fee to extend for 1 or upto 3 years.
The issue was due to the dealer not being able to access the dvla system as honda had been hacked. So i got it with a 20 plate as they could do normal registrations and then a little later, I contacted mb and they put it on over the phone no issues at all.
I already had the plates as the dealer had put them on before but could not register it.
Removing it on retention is a different matter as then it could be transfered to a different name and this will need to be done prior to the car being taken back and the new reg plates put on and the new v5 issued by dvla, especially if it was a privately owned car, you would not be able to sell it until you recieved that.
So the questions are about it being taken off and put onto retention and the leasee’s authority is needed. It’s considered an asset i guess and my guess is that they will put the retention certificate in the leasee’s name and say if that’s your wife and you want to put it in your name or it is in your name in the beginning and not the leasee’s, you’d have to transfer it to their name via the dlva using the retention certificate to put it on a car on the scheme. Guess it’s to stop anyone but the registered owner/ leasee removing the plate which is normal.