Just a thought, maybe off-base and not important:
To assist in the dimensioning of curves that look like arcs, but are out of current MoI tolerance testing range,
a small user ran script might be able to test a single arc-like curve, for planarity and arc-ness, with a broader tolerance,
and respond with a radius value, or "not an arc" message? User could add a regular leader with ØR...

https://wiki.mcneel.com/developer/sdksamples/classifycurve

- Brian