But there is no need for the pax and all of their baggage to offload for a mere fuel stop. And I'm quite certain the UK government and the US government could come to an agreement for a pre-clearance facility if it is that important at LCY.

The only reason I'm so skeptical of this is I've done an aircraft download at Bangor and it is a royal PITA. Any possible benefits of landing as a domestic flight are ruined by the painful steps the entire plane had to go through at the interim airport. CBP can and will want the entire plane emptied, and I just don't see them prioritizing the pax on this particular flight. It is great in theory, but it would be better if the UK gov't could swing the US CBP staff at LCY. Then the flight could refuel at SNN and continue on as a domestic flight.