It would be really hard to add terrain tools to our engine and keep the quality we have for the terrain, but sometimes it is still nice to layout a level using sculpting tools. I have recently been testing out doing basic layout in Mudbox before making a height map in xNormal, and finally running it through World Machine 2. This workflow is a bit awkward, but still allows us to automatically generate a lot of nice terrain data, and so is actually still faster than many other methods. Here is a comparison with the Mudbox sculpt on the top, and the same terrain in the engine:
Some small details are lost, but it is still nice to be able to have control of the layout, and work with a tool for sculpting as advanced as Mudbox. Here is the new level I am working on that takes advantage of this technique!