TCAS relies on the other aircraft having a functional transponder selected in the "ON" position. You would be amazed, nay, shocked at the amount of aircraft i see launch every day without their transponder on. and this is in controlled airspace!!! what about farmer jim out at whoop whoop station, i'm sure he does a full and comprehensive run up and ensures transponder to ALT b4 take off..not.
TCAS is a flawed system, but it's all we can do. see and avoid does not work, ATSB have acknowledged this. so what can we do? is compulsory TCAS the answer dick? really? how many mid-airs have there really been that could have been prevented with this equipment on the aircraft class that your going on about?
I'm really not sure what your agenda is here dick. I'd agree with you 100% if you included the fact that ALL transponders must be hard wired to the master switch, so they can never be turned off. however, i don't think that this will happen. but until it does, TCAS is relying on farmer bob in his C152 to turn on his transponder when he goes to check on his dam which just happens to be under final to a remote airport...
Think about it, hey?