Anton, I'd love to enable the importing of raw data by those people who have a mind to create it. Would you be looking to import airfields, or some other entities?
Not just airfields, but everything, layer by layer, time permitting. There are various mapping data freely available.
By the way, are you using just the digital 3D terrain for terrain presentation or graphic images as well? In the latter case, different users may prefer different styles, so allowing people to scan their favourite maps (or convert existing digital charts) and insert them into the program may be a good idea.