I know that coop was a big discussion that happened (and is still happening) but what about creating an add-on, download, or patch, that would allow Divinity 2 players to upload their characters to an arena/world where there could be PVP matches.
Of course this would need a lot of regulation on who can battle who and such as to make it fair. But imagine the possibility of taking your character that you've put 60 hours of work into leveling up and buying armor for and pitting him/her against another. It would be amazing and extremely fun. It wouldn't be the same as coop, but it would make the game much more interesting and open it up to more players, because some only care about playing with others.
The work to create it could easily begin after Divinity 2 has been out for a while, to see if they would have enough funds and manpower. I don't know much about devoloping, but I'm sure that creating a PVP place would be easier than creating on online MP world of Divinity 2. (But once again, I'm not a devoloper, so I could be wrong in that statement).
PVP would be sweet.