- The number of players: Popular servers on nwn have roughly 50 players connected at the same time. 64 seem to be a good maximal size.
- The number of DM: DM should take a player slot but not be limited in number. For torturing many players, we need many DM ^^. DM access must also be restricted by the owner of the server with a DM password for a certificate DM list.
Not sure but I think they where more thinking of max 4 players and 1 DM. I dont think you want to see this game played by 5+ players. Every turn takes at at least 20 seconds and that is if players play fast. Multipy that by 5 and you already need to wait 2 minutes until a player can make a next move. this will scale up fast and make it boring for a lot of players.
Multiple DM's I'm not a big fan of either. A game can be ruined fast if 2 Dm's disagree with each other.
For the DM I would split up his turn in 2 parts. One is the fase where he can spend action points. All his minions and bosses ofc have a basic amount of action points but it's very low. When he gives them extra action points the minions can do more special attacks. Placing traps, activating special triggers, giving minions a potion this all costs action points and makes sure the DM isn't to powerful.
After this turn the DM can play all the minions that are in combat.
When the DM kills a player he should also get a reward like extra action points for the next turn. Or there could be other ways he could earn actions points like destroying a chest before players reach it.
At the start of the game there should be a limited amount the DM can choose of objects that he can use during the play. Limiting the DM power should make it entertaining for both sides and require a tactical approach.
This is an interesting way to see the DM mode. For ourseft, we didn't saw the DM mode as "DM versus Players" but more as the "DM with unlimited powers is telling a story to a group of player". Multiple DM were just here to do different animation with different group of player or managing very big events.
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?
That is not nice and we can't really do something to bypass that without an huge modding of the game engine.
Without the ability to run persistent module, I don't know if it's really worth the time to do a complex DM mode. In nwn the only popular servers were the persistent ones, other with punctual campaigns were very uncommon and are now totally forgotten. Persistent module in an other side are still here and will be here for years until another game with the same ability come up.