I previously ticketed one DONE5 with QF that included LHR-HNL-LAX Also BA accepted the routing. AA didn't accepted the routing, but they promised to honour the ticket if another ow airline would ticket the itinerary. But AA said that they would not touch such ticket, if any modifications would needed.
I guess airlines that use Amadeus accept it more easily as Amadeus displays it as a one segment versus Sabre that displays LHR-LAX and LAX-HNL separately even with same flight number.

Booking HNL-LHR in A would have definitely been possible before AA recoded domestic A to D, but it's bit harder.