This particular topic has gone quiet since the April-May publicity grabbing about where this phantom is to be based. No web site, no more press releases, does anyone have any news on this topic ?
As for UK pilots flying domestic N reg in the US - HAHAHAHAHAHAHAHA, there is only the UK Govt soft enough to permit that sort of thing - ref the 1995 attempt by BA to put USAir FO's into the right seats at BA EOG.... finally thwarted by BALPA I believe - but only after BALPA had agreed to it and then realised they needed to calm down the membership ! I believe it took some discussion in parliament though...
When a US tour operator chartered a UK aircraft to fly a program from Newark to points in Africa via Gatwick, the FAA wouldn't even grant a licence to fly into the US unless the aircraft was operated under the US flag, as a result, a US operator flew the aircraft on the N reg to Gatwick, there was a reg change done in Gatwick - EVERY FLIGHT, and then the aircraft continued on to Nairobi. The reverse was done going back to Newark. Lesson learned - very protective ! Long live the Jones Act, it's a shame there isn't a similar effective law in other countries...