As Robin said... the LAST is not ICAO compliant, whilst it may get UK approval, it will be useless elsewhere.
The big question is do NATS want us all using these? A controller I spoke to said he did not want it, as he would spend too much time turning off everyone's idents, so that he could see the traffic he was controlling.
The current situation, whereby it is required for airways, class A, is fine. Class D access could be by PPR for non transponder traffic and that would be fine too. Class G neither needs it nor would benefit from it.
Unless, that is, Class G starts getting full of commercial traffic
