Quite honestly? For cRPG systems in general? Some form of AI to guide things on the fly.
Let me explain: A big part of what makes tabeltop RPG systems fun is the creative flexibility players have to come up with unique solutions to a problem. This, unfortunately, is really difficult to translate to computer games. (Just look at what happens to the poor school of illusion in every single video game implementation of DnD for the most severe example.) This works in tabletop because you have a DM who can make on-the-fly adjustments to what the players are trying out. You simply can't have that in a video game (currently.)
Larian shines the most when they try to APPROXIMATE this. Unfortunately, they can only ever do an approximation. And it likely adds a lot to development time, because they essentially have to think of the solutions themselves and code them in. For example, consider early on in the game, where you visit the goblin camp and come across a bunch of raucously partying goblins. One thing you can do there is distract the goblins with a bard and then poison their drinks. It's a pretty neat little solution, but it's one that Larian had to think up themselves first - if THEY hadn't thought of it, poisoning the drinks wouldn't even be an option.
But seeing how well conversational AI has done over the past year or so, it's made me wonder: Could we use an AI like this to sort of "DM" over the small things? Probably not currently, but I wonder how far we are from that. The overall story could still be driven by whatever the writers wanted. But like, what if there was an AI DM that could listen to things the players say they want to try, and make small adjustments on the fly to allow them to try their solutions? Maybe we could achieve a degree of flexibility closer to that of tabletop. Maybe we'd actually be able to make illusion spells feel good if a player could describe to this "AI DM" what they wanted to make an illusion of.
