Yes, any discussion that starts getting involved should be moved to its own topic (perhaps reposting the relevant info from here), so it is easier to follow, find or refer to at a later time.
Larian's next game will have a multi-player component, but there has been no information revealed about how it will be implemented. They have not said if it will be single character or party based (or single character with henchmen / summoning dolls).
Multi-character, non-turn based games do need to have some form of AI for characters not being directly controlled by the player.
My preference would be to retain complete control over all the characters (stats, skills, equipment, etc) and have an AI system in combat good enough so I don't need to frequently switch between character to adjust what they are doing (except maybe for the toughest battles). I would like battles to require some strategy, so that pretty much rules out an AI complex enough to allow autonomous party members. If I know in advance enough to set up an IA script to handle any fight, then the fights are not challenging enough.
The issue of pre-generated vs custom characters is separate from AI, except that there may be AI restrictions for certain characters (a pre-built warrior may refuse to learn magic, or a coward merchant may refuse to use a melee weapon).
It is certainly easier to create background stories, individual side quests and character interactions with pre-generated party members, but these elements can be designed (with some limitations) to fit certain classes or genders, etc, which could then be assigned to custom created characters.