The Swiss Air Force mountain airbases are amazing IRL as well as FS and of course best in FSX if you have it. Try also Saanen and my favorite, St Stephan, where they have a summer airshow and fly in Hunters and Vampires.
Willy - re AI, I see like me you make your own "designer" custom GA AI. I have a few traffic routes around selected favorite airports - nothing too extensive to save on FPS. I do it all manually using TTools rather than a package. You seem to have all the great classic aircraft absolutely everywhere you fly. How do you do that?