Here is a teaser of a series of screenshots and videos to come very soon:
This is not Minecraft on LSD.
Once you have a voxel system that is capable of representing surfaces in any direction and curvature, the real challenge becomes UI mechanics. Creating content has to be simple and rewarding. It has to feel like a game. You cannot expect players to pickup a manual or become experts in full voxel edition systems like Z-brush or 3D Coat.
But the potential is definitively there. Going off-grid allows for more interesting creations. If the system is intelligent enough to adapt to whatever is already there, you could be creating all sort of angled and curved content without busting any veins in your forehead.
What is even more interesting: there is no reason why you would limit this only to cubes. These elements you place could be anything: column disks, rocks, crystal shards, archways, statues. They could be even portions of stuff you or someone else has done before.
I'll leave it there for now. Hopefully you will be intrigued enough to come back later checking for more.