Let's say after a knife project I have a nice region that I want to extrude. Extruding outwards along the normal works fine. Extruding inwards along -Z however does not work the way I want it to. Starting geometry with selection to be extruded inward:
Dragging this down generates correct faces in the interior but also zero volume regions at the exterior:
Instead, I am looking for a final mesh without these exterior slivers. Similar to ZBrush's QMesh or Solidworks Extrude Cut:
This is obviously a simplified example where I can delete offending faces one at a time. What is the best workflow to either avoid these faces or quickly select them all?