BEagle
There are many pilots who have taken IMC rating courses, passed their IMC rating tests and continue to take their IMC rating renewals all on N reg aircraft. IMC is sub-ICAO so there is a long history of the CAA accepting sub-ICAO on N reg. I suspect this must be done with tacit FAA understanding.
You seem compelled to prove your point but I don't see why. What makes anyone using a sub-ICAO licence more of a risk on N reg than G?
There are more rewarding flights to be had than this one.