Either make only the main character be able to lead dialogues
And what happens if they're dead, but the NPC you just saved wants to initiate a conversation ending the quest?
Easy solution: let the NPC tell your companion that he won't speak with you. So you have to revive the main character first until you can progress. By the way, DOS1 functioned in the same way if only your two (real) companions survived. Most NPC refused to talk to them. You could only use one of your two main characters for most (relevant) dialogues. I don't see why this shouldn't be possible for DOS2, but for everybody in your party with the exception of your main character.
at least make dialogues dynamic which means that NPCs should remember that they already talked to your party (no matter to which char) and refuse to talk to your party again about the very same matter.
Then what about party members that were absent during the previous attempt?
Nothing. They're irrelevant. Anyway, I still strongly prefer the solution that only your main character can do the talking with NPCs and that your (AI-controlled) companions only chip in in specific situations in which there is a relevant decision to make.
And in both cases, all mechanics must remain consistent between SP and MP, otherwise they'd be effectively making two games(identical, but separate).
Yes, and that would be for the best. Because right now, the SP is just an afterthought, no matter what Larian promises. The current implementation is a coop-MP game that can also be played alone but will make much less sense that way in terms of how the narrative gameplay work.
That's imo pretty weird and alarming given the fact that the VAST majority of people played DOS1 in SP, and ONLY in SP (based on Larian's own survey during the kickstarter). It's like catering to the 10% out of principle, neglecting what the vast majority of the fanbase wants and expects. That doesn't mean that I want them to abandon MP, not at all. But it's imo not done with something like: "Hey, it's good for MP, let's stop here. It will surely work for SP as well...somehow..."
Short: if a mechanic doesn't work in the same perfect way for both SP and MP, they should indeeed make two seperate solutions or at least adjust the solution to the respective needs. Either that or SP will always remain somehow crippled and way below its actual potential. That way DOS2 will never become what BG2 was to BG1, I fear...
Once this system is integrated your companions will be AI-controlled in such decision situations (like it was in DOS1 for your second character).
Which was optional, and as such it should remain.
This time we have the "love and hate" relationship system (which was a kickstarter stretch goal). How do you imagine that to work if you control all your characters in your group in terms of narrative exploration? Making love with yourself? That'd be a complete roleplaying overkill (as it is already right now, but even stronger) imo. But well, if people really want to play hardcore coop with themselves, why not...
