If one's FAA certificate rides on a CAA or JAR licence, will 'we' (UK-based) have to go through the same rigmarole with the FAA again if/when we convert our UK licences to EASA? The cost appears to vary between £42 and north of £450 at the moment, depending on whether it's done in the UK or the US, and I'm not keen on forking out again.
Definitely, which is why you should do
standalone FAA licenses in all cases.
It's more than just money. It is not beyond the bounds of possibility that the 61.75 issue/mod route may disappear from Europe (it was never possible before about 2009, for example - you always had to go to the USA to get it issued or updated), and while I have no reason to think this will happen it would not shock me if the USA decided to fingerprint 61.75 holders or applicants. Especially if the EASA-FAA FCL treaty process breaks down, which nearly everybody I know who knows anything about it close-up thinks will happen.
When the ICAO English Language Proficiency add-on came in, Europe filled up with headless chickens running around like mad, trying to book an appointment with 1 of the 2 people who could "apparently" do it. I can't believe anybody is contemplating a 61.75 after that fiasco.