Danny, your post 7334 is tribute indeed to your dedication to this thread, and gives us all a quick reference to the differences of the A-31/35 'internals'. Your conclusion sounds to me to be the most likely explanation of the seemingly hybrid nature of EZ999's cockpit arrangements, that it was saved as 'the last of the A-31 line' but the later and better equipped A-35 internals allowed for better instructional opportunities.
Having said that, a couple of points to raise:-
First, are you saying that there was no lighting at all in the A-31, no nav lights, no cockpit lighting, no landing lights, etc? I take the point that Dive-Bombing is a daylight occupation, but the way there or back could be before daybreak or after sunset could it not? OK the aircraft didn't lend itself to night flying but war has a way of inflicting its own agenda (like a delayed RTB due avoiding an enemy fighter?). If the A-31 was so deprived, I think that the USAAF would have required a minimal night/low vis capability in the A-35, wouldn't you?
Secondly, AP 2024A presumably preceded AP 2024D (the Roneoed no illustrations austerity RAF MkIV Pilots Notes). If it was the MkIV 'master reference pilots notes' (one copy for Wg Co Flying only?) it was published with US illustrations of the A-35 generic aircraft and not the much later post-war Narellan fitted panel, modified or otherwise. I suspect that the AP 2024A illustrations are of the A-35 ex-factory gates cockpit, and as 'shoe horned' into EZ999 as you suggest. Do you concur?