Hi Jorgen - I can’t tell if you are asking about extrusion or moving … in your image the edges of the mesh look ‘extruded’, you can do that by Gumball extrude of the mountain - but are you asking about that or making the mountain from a flat mesh?
What’s not robust? Maybe that can be fixed… I imagine your script works similar to this: Dup the mesh border(s), copy the mesh a certain distance in the extrusion direction, extrude the border(s) the same distance, convert the extrusion(s) into meshes using simple planes, then join…
I imagine problems could come from having open edges inside the mesh, but you should be able to cull those by only extruding closed loops.
Of course, if you want a dynamic preview, that’s more painful.
That’s close I make my own new mesh from the edge curves by adding vertices and stiching them, and yes, it is bad meshfaces that is the issue. But sometimes the meshes are pointing the wrong way (need to run unifymeshnormals at the end, and there seems to be a bug in the rhinoscript tool for that so I use rs.command) and Rhino’s gumball drag seems to have overcome that part.
I will work on making it robust now that I know that this isn’t available for scripting.