Started a game with someone, they are no longer playing, so now im in act 2, with a hero i dont want.

I cant remove them from my party AT ALL!?!?

So i have to do main story quests twice, i have to deal with immersion breaking conversations where i literally have to restart the same dialogue and quest progress start to finish because it treats this second character as a totally separate main player character?

Why is this designed like this? Is there a console command or something that i can use to delete this character or do i seriously have to start over a 30 hour play through just to get rid of a party member?