What's the big deal? Lonely Scottish herders have been implanting human DNA into sheep for hundreds of years.
</Tasteless Joke>
Despite the ethical complications, the idea is a good one IMHO, if only for the mentioned organ-transplant advantages. What would you rather have? Your life depending on someone else's death...and possibly too late to save you? Or your life depending on the death of a non-sentient animal who's engineering to match your DNA probably will take less time than waiting for an organ via human death?