tldr: using specific save settings in illustrator and a script, we can generate an SVG file that uses embedded CSS web fonts and can have its text content edited dynamically (this just solves the font display problem, not the text alignment discrepancies introduced by the way text is layed out in the SVG, that will have to wait). Check it out - all the fonts in this processed SVG image show up just fine in Firefox and are being loaded from embedded data: URIs rather than system fonts.
This is how I'm saving my illustrator file:


