We really need enhanced terrain sculpting tools in the next version - starting with the ability to define the angle of slope for a cutting or embankment. That would be of great use using splines as illustrated above.
Besides having smaller and other shaped tools, I wonder if it would be possible to generate a topology or landscape profile using splines meant for that purpose so we don't have to re-purpose roads
Using World Builder from Digital Element as an example, the landscape shape is generated using hand-placed splines. The splines are similar to the roads and do a similar thing, and remind me of the ones in TransDEM. The splines can be placed in any of the normal CAD views - Top, Left, Right, Bottom, or even Camera view (Bottom and Camera seem useless to me, but they're accessible there). Once the splines are placed, the terrain is generated similar to us using the smooth terrain under the splines, creating the terrain topology. The lines can be moved, spline points added or removed, smoothed, etc. There are also seed values available to add in randomness of the terrain, fineness, angles, etc.
What's cool with this profile tool is these specific landscape profiles are saved into libraries for future use. Having a library of shorelines, for example, we could grab one that meets our needs, adjust the shape as needed and generate the terrain. When removing the profile from the scene, in World Builder, there's the option to save the custom landscape profile or not. There are also a built-in library that includes some really, really complex profiles such as Yosemite National Park, some volcano I can't remember, and other generic ones such as an island, various valleys, and mountains. The program was not inexpensive and required a horse of a machine to run it in its day and even then it was really, really slow, but I got the money's worth out of it for some animation and advertising projects during its day.