I think this is going to be nearly impossible to do from within a PostScript
program. If you search the group for my thread "Interrogating a font" it goes
into the kind of font information you can gather from PostScript.
You can get a good guess for certain metrics like baseline and cap height,
but others will be harder. I was trying to generate a PDF font descriptor
and stuff like 'isItalic' (boolean) was really hard to determine just by analyzing
the glyphs (at least for me).
So, probably a better course would be a language that has bindings
for fontconfig and freetype libraries. Fontconfig helps you search the
operating system for fonts using a standardized query facility, and
freetype lets you pick apart the font for any info you might need.
This may involve some hackery to heuristically convert a PostScript
font name into the format that fontconfig wants. If needed I can dig up
some C code from xpost that does this (or at least attempts it).