The Asymptote homepage may not imply utility for font design, but Asymptote is a very close descendant of Metafont. It turned out that much of what Metafont did (particularly its emulation of pen strokes) seemed more useful for diagramming than font design, and so its descendants have been diagramming software. To use Asymptote for font design, I have it generate Python code that uses the FontForge Python extension; Asymptote constructs bezier splines, and FontForge does the fontly file-construction work.
Yet to be tested is how easily and well my font design model (which is based on pre-industrial methods of type-making) can be used to define large families of type controlled by a set of parameters. Different selections of parameters would give different weights, different design sizes, etc. (which was one of the goals, only unsatisfactorily achieved, of Metafont’s pen-emulation model).