Simplify Follow path animation controls

The current Follow path animation controls are not intuitive and offer very limited control of the timing basically just start and end frames.

Ideally there would be a keyable Fcurve that goes from 0 to 1 -curve start to curve end on the vertical axis, and the time on the horizontal axis would be the frames/duraction. Keys with tangent controls throughout the curve would allow for better control of the speed throughout the curve.