I have to admit I'm not sure why you keep mentioning/involving the chain system.
Aside from the fact that on a personal note I have nothing but contempt for it and I'd love to see it expelled from the face of the planet and YEETED past the Oort Belt with a nuclear-fueled SHOVE, it doesn't really seem that relevant to the dialogue system at all, on a mechanical level.
I know you hate it, but I mention it as it’s a mechanism the game already has for the player to indicate what party members they want to act in concert or independently, and I refer you to your earlier points about reusing what’s already there and the late stage of development.
I already pointed that without an extensive revamp I think that system would have too much of an artificial feel to me. It would feel like having several parallel conversations rather than having all the characters be part of one.
Fair enough. I still think it might be a cheap way to get some approximation to party dialogue but I threw the idea out there for feedback and yours makes it clear it’s not the elegant no-brainer I initially thought it might be!
I also don't happen to think that just relying on the general rule "NPC shouldn't start dialogue on their own" could solve much.
Again, fair enough. I put it first because I assume it’s cheaper, and would preserve player choice of who engages in specific cases if there were a default face (be that the MC or a designated one). I agree there are plenty of ambush scenarios where it wouldn’t work, but would be a quick way to fix, eg, the tiefling rescued from bugbear, Sazza after opening her door, Mirkon after saving him from Harpies, Karlach as you approach her, and possibly Ethel after surrendering (as long as she didn’t heal herself!), to name just a few examples off the top of my head. But while I’ve stated my ranking preference, I can understand why you have a different one.
If we have to imagine an IDEAL solution rather than a compromise that SOMEWHAT works, I prefer the idea of "The MC/player is the core of every dialogue and NPC interaction; the companions can occasionally infer to help according to their individual competences".
Well, yes, but this wasn’t meant to be an ideal solution and, to quote another poster…
I dislike to fantasize about unrealistic or overdesigned systems that aren't practically viable on a reasonable budget, so I always try to 1) keep things simple. 2) recycling as much as I can of what's already there. Especially this late in development
Anyway I’ve chucked my suggestion out there belaboured my points enough - or too much - so I’ll stop repeating myself.