"The more problematic in your post is more the turn by turn thing. We are not very familiar with Divinity and i think we didn't even considerate that. If a pseudo real time mode like in nwn2 or pillar of eternity can't be implemented for the multiplayer, a large number of player can't happen. What would happen if a player enter in combat (and switch to turn by turn) and a player in an other map doesn't?"
It will not be real-time combat in any manner, I think that is in total stone. BUT the system was brilliantly designed to where you can have two groups in different combats at the same time and they don't interfere with one another. Or someone can be in battle and the another can be in town moving around doing their own thing. You only become part of the TB action when you are like within 30 yards or so of the conflict. So it could still work in way you allude towards.
That said, I'm not seeing the persistent world for D:OS 2. It's just too much of a difference.
I'm also in agreement that it has to come out with the game in a very solid state, if we don't like it within the first weeks, it will die in terms of people caring to use it. I'd take a strong look at how mods happen with the leading game and assume that trend to continue.
I think they should just chip away at the stone. Lets hope there is a D:OS 5 for example. Each one expands on all aspects. So we had in D:OS a mod tool, now we'll have a better mod tool and a GM Mode for D:OS 2. In D:OS 3, I suspect we'll have better Mod Tools and DM Mode yet and maybe that is when persistent servers kick in.
I'd be happy with a nice bar raise for each and every release. We've been idle for 10 years in this area, a reasonable approach per release seems realistic to me.
Some mention doing things like modifying the world live, well that has to affect everyone without reloads. They really would need to create a Standalone Server engine that feeds clients. I think that is a major change to how the engine works today.