I'm a little late to this party, but I think that Wrench's WW2 Europe terrain covered nearly all of Western Europe from the UK down to Switzerland, and maybe even Northern Italy. That would suggest map size isn't necessarily an issue and that it could be possible to make a similar slightly larger terrain that covers Italy and the Balkans too, enabling you to not only fly aid deliveries from Ramstein, but also fly B-52 & B-1B Allied Force missions from RAF Fairford all the way to Yugoslavia and back.
Not that I'm suggesting anyone should actually make such a map as I can imagine that tiling and detailing a terrain covering such a massive territory would be a huge project.