Hrm. If we are attempting to replicate a npc and only adjust a few things, then by this logic we'll need all their bells and whistles for information, yes? But the NPC at the very least keeps their home, general pathing and whatnot?
For example, if we tweak the vendors, do they still retain their stock and sales?
Semi related, could this be used so you don't get eaten in the wild by a certain NPC, or has that been fixed?
I haven't tried altering any NPCs yet, but I presume if you leave the physical and private description fields blank for the original NPCs, then they will default to the original description for that NPC.
Of course this is all new stuff, so I could be wrong, but that is the impression I am given if NPC descriptions are to be kept hidden.
You can only change the original NPCs into ones of the same gender.
However as far as I've figured, you can make it so the AI treats the character as the gender that you want by adding that detail in different ways, such as in the Public/Private Character Description, and in the character's Set Knowledge.
I don't know how far you have to go exactly, and the more stuff you change from the original NPC's original settings the more different they will become from their usual self.