There is currently no way (that I am aware of) to measure the diameter of a bolt circle with an odd number of elements in a model withough creating a sketch to construct your own circle. With the improvement of the measurement tools and the summary that is currently provided, this should be possible. If a user picks 3 cylindrical surfaces normal to the same plane, or any three points on the screen, the measurement tool should be able to mathematically plot a circle and give a diameter reading. Bolt circles would be the most common use for these, but the tool should not be limited to only hole references. 3 points, 3 axis and a plane of reference, or 3 curved surfaces and a plane if they are not cut through the same surface.
This should also be expanded to drawing dimensions as well.