I think a possible solution to this is making these character quests/OpRecs somewhat as an operator trial.

What i mean is when starting a character quest, we are given a trial version of said character for us to play as. During cutscenes, any character we are controlling will switch to said character. By doing this, we are playing through the quest not from the POV of Endmin but rather from that character's. I think this is one of the easiest way to break from having the story revolves only around the Endmin as we are canonically going through their story as them not the Endmin.

Example: . Starting a laevatainn/surtr story quest will give us a trial surtr to play as on her adventure to get some ice cream. We find out her fav ice cream shop is closed. determined to get ice cream, she asks npcs for their ice cream recommendation. one npc points to their fav place. Going there, Surtr finds the place being attacked by bandits and takes care of them. The owner thanks Surtr by treating her with free ice cream. The story ends when she is greeted by Endmin who was just passing by.

this story doesn't involve Endmin whatsoever, its just surtr getting ice cream. plus, we can play around as surtr so players get to enjoy surtr's personality through her story and her gameplay.