When I was tinkering with SDF Modeler I got the sense that spline SDFs could be even more powerful as a modeling tool if the cross section could be deformed into an ellipse. It would probably open up a can of worms about how to parameterize the curve and adjust for holonomy, though the latter part could be handled off of the GPU.
I wonder if a quadratic hermite model would be more viable for simple realtime curves...