As I mentioned in my thread…you can still use a random seed generator “and” have a map editor. Look at Earth 2140 and 2150 Moon Project. The map editor can generate a seed right inside the editor, then with several brushes you can edit the landscape further.
I would prefer grey-scale maps to generate landscapes or world-machine, but if they can’t go that far, at least look at Earth 2150’s editor and implement that.