Any environment I have that does custom fonts and glyph substitution also has CSS (or similar functionality) which can be used to make them thinner, if desired.

5.2 MB (compressed) is a big package just for some narrower boxes.

5.2 MB is for the whole set, if you are using this font in a project, you will most likely set on one type of font format (.eof, etc.) and one weight (extra-thin, bold.)

The font file ranges from 18Kb to ~600kb, with most in the ~50kb, which is reasonable for the simplicity.

Fair point, but I disagree about even that size being reasonable -- or simple.

There's a million things you can implement as a font. I have yet to see anything I think is a good idea to implement as a font except the defined glyph shapes themselves.