I am missing a feature where I easily can get points along a path given a percentage.

Similar functionality is available in QPainterPath of the Qt-toolkit:
http://qt-project.org/doc/qt-4.8/qpainterpath.html#percentAtLength
http://qt-project.org/doc/qt-4.8/qpainterpath.html#pointAtPercent

The Qt-implementation has a drawback since the step length along the path is not necessarily constant for a given percentage when the path contains several segments.

This page is useful for Bézier curve mathematics: http://pomax.github.io/bezierinfo/