If you're worried that illustrator files are too proprietary, you should really consider working in postscript. illustrator will deal with properly handwritten postscript just fine and it's a mostly straightforward graphics dsl (especially if you're mostly doing icon design). plus, it's easy to convert to a pdf or rasterize it using any number of readily available tools.

if your concern is that the tools for creating OTFs and TTFs seem to be opaque, i would suggest you look at the UFO[1] specification which represents a font as a folder containing a series of glyphs which are, themselves, a highly domain-specific hybrid of svg and postscript. the AFDKO [2] added support for UFO last month(!), so there seems to be traction on that front. fontforge, natch, has supported ufo for quite a while.

the problem with picking on fontawesome is that for icon sets to work, they usually need to be consistent and it's hard enough to get people to agree to code style guidelines, much less visual ones which are wayyyy more philosophical.

in any case, if there's a takeaway it's to look at UFO, it will at least provide you with a free and transparent workflow, but how you manage that workflow will still be a challenge.

If you (or anyone else reading this) want to work on this problem, i'm happy to talk offline since i've been doing a ufo fork of fontawesome for work lately and have accumulated some domain knowledge on that front.

[1]: http://unifiedfontobject.org/

[2]: http://www.adobe.com/devnet/opentype/afdko.html