Hi Marc, I do have a similar thing set up for this. Except instead of using Alt, you can switch between scale-from-corner and scale-from-center by clicking a corner grip (press and release the mouse button without dragging).

I've got simple rotation working now, just working on a couple of more tune-ups to that. You'll be able to do a rotation of a specific angle by setting the angle constraint in the bottom toolbar either before or during dragging the rotation grip.

- Michael