I'd really LOVE to have companions that are not Origin character.
I'd also like to have people in my party that have other goal than "cure / control" the tadpole... This could lead to very interresting side quests and to be honnest there's not a lot of interresting side quests yet in my opinion.
Many companions quests in the old games were epic or lead to epic adventures / dungeons.
Companions doesn't necessarily have to be involved in the main story or to be playable characters (and all that this implies) to ensure that players have an enjoyable experience.
yeah I miss this a lot too
Finding the temple district in bg2, taking Anomen to his dads house, dealing with his family problems, potentially changing if he becomes a paladin or not.
Keldorn, wife problems was grounding and interesting gave him an understandable backstory, the cost of Duty on the Lawful good
you can help him realise he still loves his wife, help her realise she still loves him and let him retire, you can also convince him to hang the guy she is seeing and imprison his wife leaving his kids with out a family.
some small quests from bg2 that didn't feel huge and epic or anything, but still had a massive impact on me and left me thinking about them years later.