Larian has had amazing success with crowdfunding because they have a passionate fanbase who loves their games. Divinity 2 is awesome, but I want more. I, and many others, would happily give Larian more money for announced DLC projects.
Crowdfunding DLC isn't something you see much of at all, but since Larian are titans of kickstarter at this point, I see no reason not to. Pave the way for other loved gaming companies to be supported by their fans in helping create more content for games they love.
My suggestion for the first DLC: An infinite tower/dungeon crawl roguelike mode heavy on combat. Begin on floor 1 where you'll find skill books, gear, etc. and face some challenging encounters. Each floor the encounters and layouts are randomized as is the loot you get. Every X floors you'll face a difficult boss. The objective - ascend to divinity. Rise to the top of the leaderboards by getting further than anyone else in the infinite crawl.