I know someone has done a mod that gives them idles in their packages, but that should be in anything that improves them and isn't a unique and new idea such that you'd be stealing it. Charon, Sydney and Brisa all have them in FO3 and possibly other companions as well. Giving Idle pvssyr to the companions that don't have it would be good if there's any appropriate dialogue to be scavenged. Veronica is dead silent most of the time. Makes me sad when she travels with me. Maybe better conditions on their dialogue if anything is poorly done now. Maybe improve the conditions on the dialogue around the Mojave so that NPCs aren't commenting on your missing, but hired, companions. Anything that improves their ability to stay put. I know that searching behavior is a combat behavior, but it decreases your fun as a player so I'd do something about that if you can. I'd put some kind of teleporter into your mod for calling them back to the player. If you do that it can be used to make them less annoying during that "searching for baddies when I'm trying to do something else time." Plus these companions get lost a lot more than the ones in FO3 did. I think all companions should have one. If you haven't already, make all of their clothing accessible. Make their melee weapons accessible. Make their ranged weapon available, but also provide a way for there to be infinite ammo for that weapon if the player wants it.
I have lots more ideas but I'll stop there.
:) llama
Edit: What barrettsfloyd said is true. Charon does talk to other followers while following the player in my FO3 modded version of him. He talks to Sydney, Clover and/or Jericho. It was easy to set up there. I'm not sure how it would work in NV and haven't thought about implementing something like that yet. The dialogue stuff is/may be different and haven't gotten that far with the new companion I'm making yet to see if I want to do anything like that here.