Ellipse: By Vertex and Focal Point

I would really love to be able to draw an ellipse by specifying the Vertex (starting diameter point) and the first focal point. And then see the opposite focal point appear as an overlay as I’m specifying a point on the elliptical curve.

This would be similar to using Parabola: By Vertex. Parabolas, btw, have by far the most comprehensive and useful drawing options (of all curves that use foci), and as I posted a while ago, the Ellipse command really needs these drawing options as well.