Well, Unknown_K said it all !
The A-1200 wasn't something really new and unbelievable great as the C64 or A-500 was when it was released. It was just a polished and tuned up A-500, imho. This also was the reason why I never bought an A-1200 back then when it came out.
I think C= should have released another new Computer like the C64 or Amiga was. I don't think it was a big advantage for the A-1200 to be backward compatible to the 500. For business a card based system with grafik and soundcards like in a PC would have been the best, and for games compatibility to old A-500 software wasn't necessary since there would have been ports for the new system anyways !
But this would have meant death of the Amiga, but birth of a new Commodore system instead