I think someone mentioned on the RP1 Ride thread that Amblin should in theory have the rights but I may be wrong. And that Warner/Amblin may be more willing to trust the people in charge of Diagon and Hogsmeade to throw around some ideas than an Australian Warner Brothers park that honestly should be classified as Australian Regional than anything else.
Also, if they would've had RP1 in mind for WBDubai before they began work on the indoor park, then that would've made sense.
To be honest though, and this does need to be brought up, why expand the armory for something like RP1?