Unfortunately, I think you just came up with the probable scenario - build it all here and then pack it up in pieces. It would be nice if they kept things simple. The Shuttle started out as a simple spacecraft though, and we know where that ended up once the bean counters and politicians got a hold of it.
If they can cross 90 or more miles of open water/ocean in an old Buick, I think they could probably contribute a bit to our Lunar/Mars missions :-)