Get 'em all on a list then! I actually rarely build 'Aircraft of the Aces', they're normally just 'ordinary' Squadron machines.
But we have to look carefully at what Wayne pointed out - the availability, affordability and, above all, the simplicity of building and entering. For instance, to have a build of, say, Chilean Air Force types, would be very interesting, unusual, and some colourful models of different types of perhaps not so common aircraft would emerge. But, it would probably limit the numbers taking part. However, if there was a GB for a particular aircraft, then ANY country using that type could be modelled and entered, at any period of the type's active life. That means, for example, that a Swedish Mosquito could be entered in a 'Mosquito GB'.
I'm all for some of the more off-beat subjects, but the GB theme needs to be open to, and accessible to, as many as possible - the more the merrier, whatever the skill level.
Talking of which, all you modellers out there in Cyber Space land, get your glue out, and enter the current GB!
Terry.