TBF, realistically, that would require an exponential expansion of dialog recording that would take so much time, storage, etc. it's not feasible.
Think about it: let's say a conversation is currently between the PC and Astarion, and let's say there's 3 spots where you get dialogue choices, with 4 choices each. Already that's like 64 different dialog choices they need to record Astarion reacting to.
Now you wanna include 2 more people in that also reacting? And it could be any 2 from what are already 5 options, soon to be more? And presumedly those combinations would also then need to interact with each other, and thus have different sets of reactions coded for not only each dialog option but each other potential party member?
Suddenly every single conversation requires THOUSANDS of recorded lines of dialog. Hell, they'd have to delay the game a couple years just to record all the extra dialog, and the game would be too big for most people's computers. I honestly feel like the only remotely realistic way to make this happen would be to ditch voice recording all together and go text-based.
Just because something is commonly requested doesn't mean it's feasible.
It depends how it’s done, I think. If we’re merely talking about being able to swap in other party members in the course of the conversation then they would already need to have the vast majority of required dialogue just because they could have been the controlled character at the start. So the only problematic lines would be transitions where we’re swapping them in when the previous line spoken by the NPC was specific to a different character (eg a class specific line) and therefore wouldn’t necessarily appear as a branch in their dialogue tree. I wouldn’t want to trivialise even that, given how complex the dialogue scripting already is, but it doesn’t feel like it would require prohibitive amounts of extra dialogue.
More sophisticated (and probably more satisfying) solutions that have the whole party participating rather than tag-teaming would no doubt lead to more work than is feasible, but I think it should be possible to at least do better than we’ve seen in EA.
