A little codependency all round never hurt anyone. For instance, you may have someone in your life that is very good at something, so your skills in that area wane as they take that role. I don't really see what is bad about this, it's optimization and making the group run better in my opinion. Of course if someone leaves the group there is going to be pain, but that's life.
I've had someone move in from far away and while it takes some tweaks early on, we had no problems with it in the long term. Of course I've only dealt with closed relationships where possibly there is more desire to work at something. When things are open I'm sure there is a lot of extra stuff to deal with that complicates matters further, and also gives you an easy escape hatch that some humans love.