Coff
You may not be so 'tongue in cheek' as you think. The US use single engine aircraft under their Civil Air Patrol (CAP) scheme
Civil Air Patrol - United States Air Force Auxiliary. I think your microlight might be a bit limited (no IMC or night capability) but a light twin aircraft like the Diamond DA42 with an EO/IR capability would do the job and can fly for a very long time (8hours+).
LJ
