So if EASA licence chap doesn't have a current SEP rating, are you suggesting his FAA certificate is still valid?
That's a question for the FAA's Office of Chief Counsel.
Would this mean a UK CAA issued IR(R) (IMC rating in old money) would now be valid to fly N-reg around Europe, if using a FAA certificate issued on the basis of an EASA licence?
As they do not satisfy the ICAO Annex 1 definition of an instrument rating neither the British/Spanish IMC ratings nor the IR(R) provide a sufficient basis for including an instrument rating in an FAA certificate which is a necessary condition for operating in circumstances requiring compliance with the instrument flight rules.
This position is stated in ch. 7 sec. 21 of FAA Order 8900.2A CHG 2 (General Aviation Airman Designee Handbook) [
link]:
127. General Information.
o. British National Pilot Licenses.
(4) The British CAA may issue an instrument meteorological conditions (IMC) rating. Holders of the British IMC privilege are not qualified to receive a U.S. instrument rating for the following reasons:
(a) The IMC privilege is not as high a level of qualification as the instrument rating and confers no privileges for flights requiring compliance with IFR.
(b) IMC privileges can be used only within the U.K. Therefore, a holder of the IMC privilege is not eligible to take the IFP knowledge test or be issued a U.S. instrument rating.
Peter Holt explores similar scenarios here:
License Privileges, Aircraft Registers, Etc
I think you're twisting it a little... but it's good as a thought experiment!
How? I haven't offered any of my own opinions.
Imagine two Cessna Caravans, both alike, one with G, one with N-reg... Our EASA PPL, with SEP rating, and his based-on FAA certificate could operate the N-reg caravan on his FAA cert... To operate the G-reg one on his EASA licence would require SET differences training... But, would he be able to fly the G-reg one, just inside the UK, on his FAA ticket??
Henning Grossman, legal counsel at Delvag Luftfahrtversicherungs–AG (a Lufthansa-owned insurance company) in Cologne, posed a similar question to the FAA's Frankfurt International Field Office on 2014/03/13 to which the Office of Chief Counsel responded on 2014/08/06. In summary, the FAA doesn't have a problem with the scenario you've described.
The Grossman interpretation is available here:
http://www.faa.gov/about/office_org/...rpretation.pdf