I downloaded the latest beta of Inkscape (October 13th release) from this page
and had a play with the Spiro Curves. This was my first attempt at drawing an S.
Just seven nodes are required to get a smooth curve, and it is very easy to adjust. Since it is a vector drawing program, Inkscape has lots of options that FontCreator wouldn't need — fills, colours, etc., and all kinds of line-endings. The only suitable endings I could find were slab serifs, which I used with butt line caps. Otherwise, one could use no line-endings and rounded line caps.
Font Creator would need several different serifs instead of arrows, triangles, and diamonds for line endings. It would need an option to create custom serifs too.
A calligraphic stroke would be useful for FontCreator. The stroke weight would need to change depending on the angle of the stroke.
After drawing with the Spiro line tool FontCreator would have to convert it to a filled contour. As there is no way to save a spiro curve in a Truetype Font, I suspect the easiest way would be to convert all Spiro curves to contours on saving the file. The curve could also be converted to a contour by using an Apply button on its context sensitive toolbar, rather like we currently click on “Apply” to complete a contour when inserting a new contour. Before that, the curve would be fully adjustable for shape, line ending (Serif style), stroke weight, and stroke width contrast and angle.
Possibly, the Spiro Curves could be saved as a separate data file in the same folder as the font, but then that starts getting complicated.
And here is a second attempt — this time an Ampersand with just seven nodes.