Dave, apart from the second line fighter concept, I would not mind adding planes for each side as long as it "historically accurate" (I know that is a loaded term in many respects) and kept the balance. For instance, I think the P-40M is a neat little plane, and would have some value as a quick strike fighter, but I have no idea is there were anywhere near Normandy, or it was relegated to other theatres by then.
Let me put together the updated manual with the planesets, and send you a copy, and see if there is anything that can be added.
Here's a site I've found on the D-Day Allied air forces:
US 9th TAF
http://www3.sympatico.ca/angels_eight/9tac.html
RAF 2nd TAF
http://www3.sympatico.ca/angels_eight/2tac.html
It's not an official site, but it looks well researched: official sites confirm most of these aircraft.