So the easiest way for Larian to handle this is to put a row of cities or locations in the character builder where you can check off a box. Seeing as there are dozens of cities and thousands of villages on Toril, 'other' would definately have be one of those selections. I mean, not only could a character origin be Maztica, but it could literally be another prime material plane. or limbo even. It would likely depend on how important Larian felt your characters origin is, but since they seem to be the ones instigating this conversation with these tags...
If they set it up in the character generator, then the game could exclude tags that weren't relevent to your character such as Baldurian.
Where does that list stop? Toril is a big place, w/out taking extra-planar origins into account.
