Here is the patch, coming from https://github.com/mauge123/mechanical-blender from which there has been removed any references to WITH_MECHANICAL_XXX.
The patch adds the cursor as Snap Element, and "Manual" on Snap Target.
When Snap Target is set to Manual you must first set it. (Need Snap to be activated).
The target can be set once the transform is running using the "B" Key.
When selecting the snap target, events are bypassed on modal, so you can move around the scene. Maybe some checks should be done there.
When rotating using a manual snap target, you can rotate using the resulting axis between both points, pressing "W" key once the target is selected.
Also when you are selecting the snap target, you can set it directly to cursor using the "C" key.
The patch does not implement the multiple option, and the center selection during transform for scale and rotate. I'll work on this in a near future.
Any suggestion are welcome.
some videos uploaded