I agree woo.
It's going to be hard/impossable to police people checking in say 8 x m's, but have crews with s's on board to swap straight after stages. With 8 tyres it's now a 600km sprint for the cat7+ cars. The cost is the main killer though, I know a lot of people only own 6 rims on the same size, so it's not only extra in tyres, it's more money on rims. It's easy to say "just run 4 or 6 tyres", but if you want to attempt to be compeditive you will need 8 tyres.
I know it was bad enough last year with accusations flying about people running 7-8 tyres when it wasn't normal to see cars up in the air.