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.
Targets and suspect A/C
Acquisition; Radar balloons, net worked.Dual purpose G & A.
Burt's already build one:
ARES (Model 151) (Scaled) 1990 = Acronym for "Agile Responsive Effective Support." Canard configured ground attack aircraft with P&W-Canada JT15D-5; ff: 2/19/90 (p: Doug Shane). Engine inlet was on the left side and a 30mm cannon was mounted on the right side. Company working name was "LATS." POP: 1 [N1515C].
The ARES first flew on February 19, 1990, with Scaled test pilot Doug Shane at the controls. Since that first flight, the ARES has flown more than 250 hours, and demonstrated all of its design performance and handling qualities goals, including departure-free handling at full aft stick. During November of 1991, under a contract from the U.S. Air Force, initial ground and flight (air-air and air-ground) tests of the GAU-12/U gun system installed in ARES were performed, with outstanding results.
(various online sources) + http://www.scaled.com/projects/ares.html
Let's just use the Civil Air Patrol like we did in WWII.
Cost $100 and hour to put up a C172 with volunteers.
Off topic somewhat, but, I saw that the Navy wants this, the MH-60S helicopter, a multi-mission platform the Navy will use to replace the HH-60H Seahawk helicopters.
Armed Helicopter Weapons System (AHWS) {pics @ link}
Weapon capabilities include eight hellfire missiles, carried on external weapon system wings and the AN/AAS-44C forward looking infrared system. Additionally, the mission kit will give the crew capability to fire FN-Herstals laser-sighted 7.62 mm guns from the port and starboard cabin windows and laser-sighted GAU-21, 0.50 caliber guns from the port and starboard cabin doors.