For TCAS to be effective
ALL aircraft would have to be equipped with transponders. Many (like mine), either, literally could not be so equipped, or financially would be deemed not worth the expense and scrapped (or exported/stored/displayed). There isn't a portable unit available that is small enough or safe enough for use in
ALL aircraft, and I can't see that there ever will be. The CAA are happy to go along pretending that the market will make one available for a few hundred quid because it suits their argument. They couldn't give a fig if there's any truth in what they're saying, so long as they get their way and get to suck up close to the airlines
maybe?.
So, for TCAS to be of any real use, we will have to not grant exemptions and accept that many of our lovely older and more interesting types will never again grace our skies, and that the gliding and microlighting fraternity will be greatly reduced (and may even be forced to pack up due to fewer members).
I doubt this will happen, and I doubt the CAA really think it will either. They are bound to have to grant exemptions, so the question then is ... why make mode S compulsory for the rest? If not all aircraft are equipped, there is no safety benefit for us as TCAS is useless. Also, airlines would be on very dodgy ground operating outside of controlled airspace with passegers, as safety would be much reduced. So, are they offering to allow transponder equipped aircraft into previously forbidden airspace? ... Nope! So I see no benefits to us at all, and dubious benefits to the airlines ...
unless?
There's either a future plan to increase the areas of controlled airspace and squeeze non transponder equipped aircraft into smaller and smaller areas (advantage to airlines), or, plans are afoot to
maybe introduce airspace usage charges for GA ... or at least, introduce the framework to make this possible at some point (advantage to the CAA as it will be able to justify its otherwise dwindleing existance to goverment and protect its future).
Who knows?
SS