This is nice, though I think the use of indices instead of stable identifiers might bite in complex models that undergo changes. I've been toying with the idea that you could specify a point (2D or 3D in some coordinate system, depending on context) and pick the face/edge/point closest to that as the identifier. The only other alternative I see is diffing old and new, and trying to match the outputs of each operation geometrically, but that would produce extra output that needs to be persisted...
E.g. when splitting a face in OnShape, I might have to redo a whole bunch of operations later because the identifiers change, but I'm often surprised how good it is at matching up faces after a single operation. Like modifying a sketch, then having to add the new face to an extrusion, but then it magically does the right thing for chamfers and drafts.
