My fault. i never saw that the "uncertainty marker" is there all the time...
When there is a good signal it is just smaller than the position marker and i never zoomed in enough to see it

So what i was actually asking above is to give the uncertainty circle a minimum size larger than the position marker so it is visible all the time and gives an additional contrast between map and position marker.

If the uncertainty is greater than the minimum circle size, extend the radius and fade it into red until signal is lost.
Does that make more sense?