Why has no-one ever created a graphical user interface for Metafont?
One can easily imagine a system that would allow interactive adjustment of the font parameters, with near-real-time display of some sort of preview (a single character, or some chosen group of characters). I would guess that Metafont's production of bitmaps would be fast enough to support this style of interaction on a decent modern computer.
Most people would want a PostScript (outline) font as the final output, not a bitmap one, but this conversion could be done later -- bitmap output is fine for previews while you're fiddling with the parameter values.
Is there some fundamental technical difficulty here (I don't see one), or does the programming task seem too daunting/laborious, or what?
In short, two questions:
Would the development be difficult? Why?
Would the result be interesting/useful? Why?