They would have also avoided the problem of bleedless systems all together, if that is Airbus intention.
Modifying the GEnx or Trent 1000 for bleedful ops is simple, simple, simple. You just add the power offtake. There were articles originally when RR
announced the engine family that it would be an effortless mod to offer it on Airbus frames with bleed air systems.
Right now, the power offtake is a generator. You can make a bleed tap replace that without much effort. In fact, I think the generator itself uses engine air.
Are there (legal) restrictions as to which airplanes can be powered by these engines?
The GP7200 is bound by agreement. Its only to power the A380 and potential 747 derivatives. The Trent 900 no problem.
The GEnx and Trent 1000 were launched almost 7 years after those engine types. They'll be WAY more efficient.