Surprisingly the line is actually difficult to make a control of. Visual Studio is designed to work with everything in a rectangle boundary. The line completely throws out this concept since it only uses 2 points. I've seen the source code to the power packs and it is much more complex than you would first think.
I hear you, you are much more expert than I.
Just saying that the ability to draw integrated and animated "basic shapes" like lines is, to me, as important than making the other objects look nice, which they do.
As you stated Visual Studio does have lines, in the Power-Packs, can't you use that source code and develop it into animated controls?