Apparently there are named settlers scattered across the commonwealth that you can recruit. In doing so, if you assign them to a level 3 vendor, it will be upgraded to a level 4 vendor that can sell even better gear.
For example: Ann Hargraves
Who and where are the rest of these named settlers?
Also, how does this affect the stock when you have multiple vendors of the same type?
The vault tec rep boosts whatever vendor he's assigned too but not to the level of a level 4 vendor, what happens if I have him and a named settler assigned to the same type of vendor?