Another reason why I believe this hasn’t already been introduced is there’s always a question mark over any used car’s identity and there’s always a risk that the car that a disabled customer could be driving had previously been in an accident, not maintained properly or indeed out of warranty.
At least with a box fresh brand new car there’s no history of any previous accident damage (Or you’d hope not) or indeed the likelihood of anything going wrong is much lower.
In my experience on the scheme, the latter is totally irrelevant because I’ve always been supplied with complete sheds from stock that have gone bang almost immediately but it’s still less likely to happen with a new car.