Would it have Tornado capability? After the initial Baby and Super P.45 there would be Mk 2 versions with the RB.199 replacing the Spey.It would have to be re-designed and modified so much it would be an entirely new aircraft. So it would end up being a Tornado-sized aircraft...
Another advantage I though a Spey powered P.45 would have over a twin Adour aircraft, either the OTL Jaguar or the twin Adour version of P.45 was that the engine development costs were already absorbed by the Spey-Phantom. AFAIK the Adour was specifically developed for the Jaguar.