I think the ucav air dominance system should be made of multiple systems.

– A large B-2 sized ucav with an immense, powerful radar.
– Small, fast and inexpensive missile delivery drones which zip around up front firing on targets designated by the radar drones. The large ones refuel the smaller ones maybe?
– Small missile-like drones which can be fired stealthily well into enemy territory. They find themselves a nice inaccessible vantage point to land and provide constant visual tracking of aircraft flying over them for early warning. For carrier fleets, these could be small, floating boueys.