sure is. just script the loading device as an activator. (ie, a door) then just move the character into the appropriate world space (ie, *region*) according to what the script decides.
As far as the ENTIRE world space, no, you only get one of those - that's just how the engine works. But the world space itself can be very, very, VERY large. You can -easily- have a dozen different fallout 3 wasteland sized world maps in the same world space with no visible connection to each other. Keep in mind, you may need to do some hot-editing with FOSE functions to the game's INI to make this "pseudo-multiple" world space thing work.
Also depending how 'large' your world space is going to be, you may be better off just using large-scale interior cells with a skydome. Most of the downtown DC areas are actually interior cells with a skydome, for instance.