Well, yes, you can forward Bitcoins without risk this way. But it doesn't solve the real problem, which is selling something for Bitcoins that you can't get back if the Bitcoin transaction is rejected.

One online gambling site that accepted zero-confirmation transactions was burned by double spends. The bettor would quickly respend any funds they lost, invalidating the payment. If they won, they let the Bitcoin transaction go through and accepted the winning payment.

This new "zero confirmation" scheme wouldn't protect against that. It would just prevent placing a bet, winning, accepting the won amount, then canceling the original payment.

Back to the drawing board, zero-conf people.