We know they will be in for exposition and some basic pricing. Its going to be critical to round out and balance a lot of places as the NPC's listed are almost random or incredibly niche. Exposition is about setting up the world for play in the game and the NPCs aren't cheap (3 non specialised professions like farmers for 400 EP) so you really don't want to get a lot. From memory, I have no one either in notable or normal professions related to running, defending etc etc my border capital - I however have a LOT of animal related professions! On that basis to make it even vaguely normal I'll definitely need to get quite a number to flesh out the place. Of course that also means I need more parcels (and farmers) to support those new people. ;)
Limitations on the NPC's by account just make no sense as whats unbalancing in a hamlet is a drop in the ocean in a capital.