I never tried to extend the party size limit, but I was switching through group members like a fiend! I would have loved a dialogue option for dismissal, like "Go back to camp, and tell [companion] to meet me at [fast-travel point]." Instead it was drama, tantrums and heartbreak every time.
This is relatively new, but if you go to camp and ask someone to join you, you can tell them who to replace. No drama
