Green Granite,
Your question/proposition is very reasonable, but when you take into account the requirements of CAP 722 (shortcut in one of my previous posts) it becomes clear it's not that simple. Millions have been spent exploring exactly what a system that satisfied CAP 722 would look like.
Other considerations for a mil UAS include, how would a stealthy UAV be 'de-stealthed' for flight in the ATC system and then 're-stealthed' in theatre. That aint easy either.
Sun Who.