A good character need to feel human and coherent, but also have a role in the story they are a part of. You, LC, from what I gather, value the human part, the organic feeling, the credibility of a character in his actions and reactions. I ( and potentially LAcrymas ) want them to tie nicely in the story, play their part, justify their existence storywise.
I don't disagree with that one, not at all. But from what I gathered so far from the vision for DOS 2 (and the solid information we have on how DOS 1 played out) there will be some severe shortcomings to that above definition of "characters that feel human and coherent". I fear that my side of the companions (like you quite fittingly outlined above) will either be inferior to already existing CRPGs or don't exist at all (mostly to basic design vision, favoring co-op MP). But to explain that in more detail I might first have to point out what a "human and coherent" companion actually means for me aka the requirements to make one believable and lifelike:
1) Predefined race, gender, look/face and voice.
2) Predefined occuption/job/skillset.
3) Own convictions, goals and genda.
4) Believable backstory/origin.
5) Believable and lifelike behaviour, following own agenda.
What does that mean for the companions in game? What are they supposed to do?
1) Only following the PC if its in their own interest.
2) Voicing their opinion about PC's actions.
3) Getting in personal relationships with PC and other companions, including conducting dialogues within quests or outside of that.
4) Taking more "drastic" measures if PC acts completely and severly against their convictions like leaving the party or turning against the character.
5) Being able to become part of the narrative outside of their "companion job" (like turning against the player at a certain point or being killed/kidnapped/..., see BG2 for reference/example).
6) Conducting ambient chat (a lot of the party atmosphere in BG stemmed from that one alone imo)
I don't see how Larian's "companions" for DOS are ever supposed to act that way. That's also pretty much impossible since you obviously can't exchange them. They start with you and stay with you until the very end with no chance to dismiss them (or them leaving you) and just trying to find a new companion. That severly limits the depth and range of possible relationships and interactions between companions and the companions and the PC. So Larian indeed probably tie every companion (which means all THREE, not more) to the main narrative (which is good for what you want) while taking away much of what made traditional companions all great in the first place. I mean in DOS you could already change your real companions quite a bit, making a paladin a rogue or a mage a warrior or whatever. That already harms the believability of said companion, making him a mere gameplay tool instead of a narratively-driven real person. What's the different to DOS2? In DOS2 everything besides the origin story will probably become aritrary in respect to companions. And even their origin story is limited by the simple reason that you have to stick with them no matter what and that no matter what you do they will always support you. How is that - in all honstely - more believably tied to the main narrative and how is that supposed to create more believable companions? I mean you criticize companions of BG2 not to be too closely tied to the main story although they are quite reactive to what you do in the game (simply based on D&D's afflictions system of course) with all the expectable consequences. Nothing of that will be true for DOS2 if SP will be like MP, just with "origin story bots".
So please forgive me, if I don't think that Larian will combine different aspects of companion design. They only try to improve your "2nd character in DOS1", so to say with giving him an origin story (instead of the player roleplaying everything himself or giving him certain traits), scrapping the real companions you had there (at least if I understood their design vision in the correct way). I don't see how that what I want is served here - like at all, I'm afraid.