I have no such objection. However, regulations do not necessarily have to change in a manner that requires any new work to be to a different standard than that of the majority of the the installation. For example, as I've said, a new requirement could relate only to 'new installations' (however defined).Just what is the root of your objection to the principle that when the regulations change everybody has to comply with them?
Utter nonsense.That is such a fundamental change to the basis of how the regulations work that I am now convinced, beyond reasonable doubt, that what you really don't like is the whole idea of regulations changing.
In many safety-critical fields, there is not this confusion of "non-retrospective" regulations. If, for example, the PTB decreed that seat cushions in airliners had to be made out of some new ('safer') material, that would not usually mean that only newly-installed cushions had to comply, leaving potentially hundreds of non-compliant ones still in the same aircraft as the few 'safer' ones. If they did accept a situation in which, say, two 'safe' cushions existed in the same aircraft as 248 which were now regarded as 'unsafe', there would, IMO, be something very questionable about their reasoning.
Kind Regards, John