Something that I think would be beneficial would be to allow for curves (maybe surfaces too) to be colored. This would just be cosmetic. Instead of a jumble of overlapping black curves that can't be differentiated in a 2D view, coloring them would make things obvious. I don't know what implication this would have on the file format. I don't know what should happen when you join to lines with differing colors.

Points and dashed lines between points should probably also be colored based on the curves color. Coloring the points would allow for multiple curves to have points visible with a reduced worry of accidentally selecting the control point for the wrong curve.

I Love MOI