There's someone successfully done so but it's difficult as it involves heavily on eventing. I wouldn't recommend it if you're not super good with RPG Maker yet. Making party member following you is much easier.
Viewing post in [ANSWERED] Character swapping?
Admittedly I'm not familiar with the newer stuff yet. I'm waiting to get MZ at the moment... Sales and all that. Most of my experience is from the older RPG Makers. But that aside my goal is actually making two campaigns for my game. I already found a new game+ plugin which should suffice for that function. Each campaign would have different characters. One would have a solo main character with a NPC follower which would fit with what you're suggesting. The other main campaign would have a team of characters. One main lead but with multiple allies he meets along the way whom I was hoping would be able to swap between for a fun dynamic battle system.