We have something like that with AEW UAV I think.I think such a 200-ton class AEW aircraft might make sense for counter stealth applications. A huge VHF-band radar mounted in E7-style should achieve good ranges against stealth aircraft. And the movement of aircraft itself could be used for ranging. A large 360 degree IRST system could be added as well.
Would be quite exotic of a system, though. And if such a counter-stealth AEW is being pursued, it would probably be classified until the late-stage of its development.
Aside from that, KJ-500 operates in the L band. If KJ-600 is anything like E-2D, it would be operating in the upper range of UHF band. All of which should have fairly long detection range against F-35.