Quite honestly, I want it to to be a LOT like the original Divine Divinity. It combined an open world and interesting quest structure with the loot and item system of a roguelike action RPG like Diablo II.
People have already talked a lot about the open world, so I will concentrate on items:
Please have an item system similar to Divine Divinity only with more types of items and more unique one and artifacts. This adds a lot to the RPG experience and was done well in DD. Please make this a priority.
Other than that, I really trust you to get it right. I think you learned a lot from DD and BD and will make DD2 the best it can be. Cant wait to hear more and play it!