Not being a TCAS type of flyer, I have to ask whether you J boys really think such a system has a place as a LL CWS on fast-jets doing 420 kts+ head-on? We also want to avoid puddle jumpers and helo's above pipes and pylons around the next corner. Is a TCAS/IFF based system ever going to detect and cue fast anough to respond. And any such system is totally dependent on some suitable kit on the other ac.
I guess the only really safely reliable high-speed LL CWS system would have to be based on satellite technology or something.
Have to agree with prang that its amazing nobody has come up with something yet for FJs, but then again I guess producing a ML CWS (a la TCAS ) is a doddle compared with a LL system.