ohohho, I couldn't sleep at night, all I could think of was an idea with the merge shaders. So I opened up terragen and this happened. Finally, the first time ever I actually managed to create a rock I imagined. Rocks, sand dunes, dirt, cracks , everything.
I will copy these node networks and create some size- colour variations, then use it on a world machine terrain with flow and slow and deposite maps. I think with the WM makro- and terragen's micro abilities it'll be quite nice!