If I understand what you are looking for, you want to hide NPC names until you have been introduced? Everyone is a stranger unless they give someone their name? An interesting notion.
Well, even if this is not what you were looking for, I thought it would be worth suggesting a place to start.
First, you would need to override the "Name" property to blank it out. Next, you would need to create a way to show someone's name only to a certain group of people. Perhaps using the "DisplayTo( Mobile m)" method, if that exists. There may be one similar. Someone who still runs a server and does active coding may be able to help out there. The other thing is that each Mobile that will be using this method must store an array of PlayerMobile values who "know" who they are. This would allow you to simply add a player to that array once they have been "introduced."