That “temporary pivot” is called “Center” in snapping options (Snap With). The idea is:
- you snap the 3D cursor to the vertex you wish to be your base point
- you enable vertex snapping, set Snap With to Center
- set pivot point to be 3D Cursor
- move and snap as you want
There’s a patch in the works that should make base point snapping much more convenient, but for now we have the process as described above.