While I would surely love Minthara to become a companion that we can actually have in our party, what I am more concerned with in this particular thread is camp followers who liven up our camp and have backstories of their own, but are not recruitable in that sense (like Barcus Wroot, the unfortunate deep gnome).
Such characters would likely require less development time and work than fully fleshed out companions, and I think they are important to your game experience in a different way. In short, they make your camp feel more alive, they make your actions (whichever you are taking) feel more impactful, and of course its always nice to have company.