Of course I want a better writing of companions, but this should be automatically the case for DOS2 anyway. EVERY companion will directly come from an origin story written in such a way it should be elligible as the main story, making every character a potential lead rather than a "mere" companion.
This is a blessing as we will be able to both get a story we are interested in and a character that will fit the design of the party. Yes, min-maxing IS a reality in cRPGs. Even on good ol' P&P games you'd at least try to agree with the other players on a balanced team before undertaking the DM campaign. Or you could go YOLO but just meet your end at the hands of some low level monster somewhere in the beginning, which is part of the game, sure, but not very productive.
It's not a mystery now that I can't care enough for handcrafted companions unless they really are tied to the main plot. I can't care less if they react to what I do or what I don't as long as I'll see them as simple placeholders, nothing more than some more stats for my character with a side-quest to go with. I have to admit I liked Liara+Garus in my ME playthrough, but really all they contributed to the game was a little quote here and there. It could have been anybody with me, it wouldn't have make a difference. So well, let's just take the companions that actually bring something gameplay wise if they have nothing to contribute storywise. Which isn't very different from getting a blank slate party right from the start. Hell, I can even relate more to Sir Pimpalot, the Rose Mage, as I created him with a backstory of mine, than to Grakkarian the Red Mage of the Fiery Hells, who I just tell to shut up everytime he addresses me because he annoys me but I still need my mage in the party. And it can be worse : if there is a risk he would want to leave because I constantly shut him up, I'd have to pretend I care just because I need my Mage. There would be a strong dissonance here between what I want and what I need, because, in the end, I have to beat the game.
As a completionist I tend to do every sidequest, so it's not really that I don't like sidequests. It's more that, as I mentionned, I don't see a real difference between the random NPC that will ask for your help and a companion, except that I need the companion to be able to beat the game ( unless I mastered the game and am able to beat it with one char, which IS a fun challenge too ). This is very diminutive of the companions, but still a reality in most of the cRPGs I played. DA:O is one of the titles that come to mind where they actually succeeded in getting some of the companions to be important characters in the main story - namely Allistair and Morrigan. They had a real part to play. BG was about the Son of Bhaal and His Inferior Friends.
As I said, I trust DOS2 should be able to bridge that gap. Heck, I don't even really consider the 3 other party members to be "companions" but rather "full fledged main protagonists" in their own rights. I don't see them as another Khalid, Garrus, Leliana, or even Adora. This is all thanks to the concept of the origins stories.
And all this comes by no mean against the vision of DOS2. After all, it tries to emulate a P&P session where every player will not only have the interests of the group at heart but also his owns. And when those players will make their characters they probably will discuss who will hold which role in the group. Hence, balancing the party beforehand. This can translate very well and easily to SP.
But really what's the matter with allowing people full control of each member of the party? As I said it probably only requires an option when starting the campaign, choosing between 1 to 4 customized characters. This WON'T break any of the writers work as the game is designed from the start around the idea that there is NO handcrafted companions. No Adora this time around. At worse, a Single Player could ask a few friends to just drop in his game, create the characters he'd like to have, and then leave. Voila, 4 custom characters. At this rate, let's just give the Single Players the ability to do just that.
BG never "suffered" from the story for specific party members. You were never forced to engage into them anyway, with a few (meaningful) exceptions.
Maybe it didn't suffer, yes, but it didn't strongly benefit either. And you say it yourself : we were never forced to engage into them.. Because they didn't really matter. Have them or a blank party, story-wise the difference will lie in the fact they have a sidequest to offer at some point and maybe a few vaguely relevant quotes to offer during the course of the game.