Does anyone know if the SDK allows people to create missions and/or flights where things are scripted to happen along the way? I remember this was a big thing with FSX - you could download all kinds of journeys like that. I remember one mission where you're flying out over a misty sea when a GIANT iceberg appears out of the gloom, and there's a sort of archway or opening in it that you could fly inside, revealing a secret base complete with landing strip. 

Yes, although currently the full content of the Mission Editor section in the SDK docs is "TODO".  If you look in your Official package directory, you can see that the tutorials, bush trips, and landing challenges are all created as missions, along with the good old spb file extension.