Zendikar was designed as a DnD esque world, and I do like the verticality of it ... lots of flying mountains and variable geography as the Roil alters the world around and under you. I know it got a Planeshift write-up, but I could see a fuller treatment as well.
I'm also intrigued by Kamigawa in its current cyberpunk era.
Tarkir would be an interesting one. I like the world, and there's Dragons aplenty, but I'd see this more as an Adventure Path about running a covert resistance to the rule of Dragons.