If you haven't seen it, take a look at https://cartographersguild.com/showt...t=33087&page=2 because it was a similar sort of process that started with contours and I abused mbartelsm's map using Wilbur. There is also a bonus technique for generating the sort of uniformly-eroded and deeply-incised areas typical of the European Alps. These mountainous patches can synthesized in any desired shape and then used as a bump map in Photoshop for more texture (or lightly blended onto existing mountain areas).

Wilbur's erosion tools are generally lossy, so you're going to see things get a bit smaller (that is, areas at a particular altitude are going to get narrower). Sometimes, using an exponential adjustment with a value just below 1 (around 0.9) can bring things back up to close to the initially-specified values without too much loss of volume.