Thanks Michael, I see what you mean about the added clutter. I had that realization when I mocked this example.

There may be a few ways of adding switching of something like that (contingent upon the attractiveness of such a feature),
Another UI icon would be undesirable for obvious reasons. Especially, since it would take as many steps to activate it as it would to use one of the dedicated scaling/rotation features already in the UI.
A keyboard shortcut would be most logical as it would be out of most people's scope of normal use. Like you said, it would have to turned on when needed.
Maybe a timed mouse-over... We'll, it's in the idea bin anyways.

And yes, I use the mentioned circle rotate with center axis control religiously, and by choice over other methods. Corel employs the movable axis, so it's second nature.