Mathematics tools

The font face is hard-coded, like you say, but it's not impossibly hard to modify. In fact, Appendix A of the full mimetex manual at http://www.forkosh.com/mimetexmanual.html contains (somewhat elaborate) instructions for modifying the existing font faces, or for adding new fonts or new sizes of existing fonts. The "adding new ones" part is actually a bit misleading. You could add new font sizes without changing the code, but new font faces would require some code changes to recognize corresponding font selection commands like \mathnewfont{stuff rendered in your new font}.

In any event, it's a bit of an undertaking. For example, I've been wanting to add LaTeX's cmmib (for \mathbf{}) fonts, but haven't found time.