Theoretically there is no need for 2♦ as forcing Stayman. You can always have some sort of relay system after regular 2♣ Stayman to handle the GF hands you would use 2♦ for. That said, if you're using 12-14, 10-12 or a similar 1N range and have decided not to use transfers using 2♦ as GF Stayman can really simplify your bidding system.