gives indeed excellent control for translations, but what about scaling and stretching? You're not using the handles for this, so how is Inkscape to know which transformation to use? BTW, perpendicular and tangent snapping will be difficult with our current mechanisms, but the other modes are either already there or easily implemented.
I'm not sure I understand the distinction; if the cursor is above the snap point it will translate the object. If it is above a handle (which is why these have to be outside the perimeter of the object) it will either scale or stretch.
I can only speak for the this approach which corel uses, but it seems to work very well. A second click on the object switches to rotation mode, and the centre of rotation is represented by a circle which can be moved again using existing snapping points
The only thing which you can't do is to mirror an object using an arbitrary line - only x or y flips are possible. In CAD software the mirror line usually has to be drawn after the mirror tool is selected I think.
Kindest Regards, Alex