All this talk about SAM batteries and interceptors armed with AIMS, Sparrows and Sidewinders is just plain overkill. The old A-1 Sky Raider would be very effective against small craft as well as ground traffic. Save the fast movers for regular A/D.
I can see a couple Sky Raiders on strips a couple hundred miles apart fed by intel from a Balloon net.
I'm sure Burt Rutan could come up with something that would fit the bill quite nicely. Still I'd arm it with at least air launched stingers, just so the pilot could stand off a bit. Guns too of course, at least .50 cals, maybe a 20mm gatling type cannon.
Don't discount the speed aspect too much though. It allows for fewer interceptors to cover the same territory.. or to cover each other somewhat if a large number of "targets" should present themselves.