There is a simple way to deal with this which is the way that certain states in the US base their law such as Florida for example, In the state of Florida all used cars are sold "as is". The only warranty that they come with is the manufacturers warranty if that is still in force. The average used car dealer does not have to offer any warranty whatsoever only to make sure that the car is described correctly and not misrepresented, for example all accident damaged or ex rental cars must be declared but there is no onus on the dealer to offer any form of mechanical guarantee whatsoever. In reality most dealers will either sell or give away an MBI type warranty but they are not obliged to.
Its a simple system where everyone knows where they stand from the word go, it is up to the punter to check the car and make sure he is happy. If you want a warranty you buy one otherwise you are on your own. I have several good dealer friends over there and they can't believe their ears when they hear what we have to put up with over here, although every state has their own laws and I believe some give the public much more protection.
It will never happen over here in a million years because of our ties the the EU but just imagine how it would transform our industry if a law such as this was implemented, the small claims court would suddenly be a very quiet place.
Just imagine, you sell a car and as soon as it is driven off your forecourt, you can be 100% sure it will never be your problem again, Heaven!