ATG, Welcome to the fray! You have researched the issue most assiduously and I commend your effort but must sadly, though perhaps predictably, politely disagree with your conclusions. The difference between aircrew and supernumerary crew is that the former is required to operate the aircraft normally, to include CC with passengers (or without CC if just Freight/Empty/AAR), whereas supernumerary crew are not. Thus PJIs are required to drop Paras but are not required simply to fly them (and yes, I know they are Honorary Aircrew anyway). Ditto Despatch Crews for Supply Dropping. Just positioning the kit they aren't needed but to drop it they are. Ditto Gnd Engs for down route support etc.
Of course RAF CC are not said to be Aircrew, I know that and it is what most of this thread has occupied itself with. I still insist though that they are Aircrew by definition (and thank you for the link!) :-
Aircrew.... Persons having duties concerned either with operating or the flying of Air Systems or with passengers or cargo when in flight.
Ipso Facto as Anthony Hancock might say!