Why simulate the TCAS?
Can one not purchase a commercial TCAS unit and lie to it about where it is and how it's moving? (Ignoring the cost of such devices, of course).
It would seem that if one has the heavy lifting done by the unit, needing only to control its inputs should be a much simpler proposition.
Hmm. Worst case, I suppose, is a unit on an actual in-flight aircraft, either piloted or not, that sends signals that translate as 'crash on me' instead of 'run away, run away'.