Bartosz suggested that we look into using data URLs without base 64. An example is http://jsfiddle.net/SJjJb/1332/ , a text-based one for SVG.
Some escaping is practically necessary (e.g. at least %23 for #). It is not clear how much is required by either browser compatibility or the standard.
He mentioned http://software.hixie.ch/utilities/cgi/data/data as a library for this as well.
If the required escaping ends up inflating it (e.g. if we have to escape < and >), so we need to calculate (either in general, or in a case-by-case basis), which is the winner (base 64 or escaped text).