On the big bombers, it might be possible to use multiple figures/props for the interior. I have, a few times, seen inside large military aircraft, and you can't really see all the interior at once. The Lancaster Navigator and W/Op positions are pretty much invisible from outside, for instance. Some way of opening up the fuselage, a little like a film set, would be useful, but it all gets complicated. I know there's a guy out there working on RAF aircrew uniforms, though I don't know what there is for the USAAF.