I'm usually loath to tout my own mods, but I feel I should bring up something I made recently, before it goes down in the ocean of time unnoticed. I did it to see if I could, mostly. It's a way to play someone other than the Bhaalspawn in the BG saga - in the first game for sure, anyway. You can appoint another NPC as the main character, and he will be the one to get all of the dreams and powers and the game will end when that one dies, and the character you create will be a companion. You could also roll up two characters yourself, I suppose, and play some kind of duet. Here is the link: https://forums.beamdog.com/discussion/66411/a-lark-play-as-someone-else#latest
It's a good idea to check out the General Modding board more often, by the way. Things get posted there all the time.
Now, as I warn in that thread, this way of playing is experimental, but through the first BG until SoD, at least, I'd say you are 99.9% safe. In sequels designers have the habit of dispersing the party as they like and only let players keep the main character, or the one they assume is the main character, so before SoD and BG2 you should use the ring again to make the chosen character Player1. Once you're over the fence in those games, you can repeat the process to travel as a companion again. Preferably not Imoen's, though, with her getting kidnapped and all. Let someone who stays in the party be Player1.