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.
"Other" should certainly be in the list of available options.
Even better would be "Other —please write you place of origin here". The same way as you can freely write your name when creating your character. And with all the same implications : no NPC will voice it, but you can select dialogue options where the variables CHARNAME and PLACEOFORIGIN are replaced by what you selected at character creation.
