Some others that are useful:
South part of the map,
-> Timefall Farm, for MULE scan negation and Human detection, get up to 3 stars
-> Cosplayer, for better backpack pouches, get 3 stars
-> The Collector, for the backpack cover(assuming he doesn't glitch out for you), get 2 stars
-> Weather Station for for the floating carrier level 2, get 3 stars
In the mountains,
-> Distribution center north of Mountain Knot, for the spare ammo pouch, get 3 stars
-> Roboticist, for the All-Terrain Exoskeleton level 3, get 4 stars
-> Waystation North of Mountain Knot City, for the level 2 armor plates, get 3 stars
Most of the other really useful stuff you'll get through story missions you can't miss.