These ideas have been superceded by the How-To describing a GzipXMLSerializer
Cocoon and Apache mod_gzip
SVG, like all good XML, can be read by humans. The cost of this, of course, is that SVG documents can quickly bloat out to hundreds of Kb, often too big for communication over the average web connection.
The SVG specification has a solution, though: every SVG viewer must also read SVG that has been compressed with gzip. In my experience, this process results in a 60-80% shrink, slimming our untenable documents down to a doable tens of kB. What's needed is some sort of automatic filter that takes svg documents coming out of Cocoon, and gzips them on their way. As it turns out, that's exactly what the mod_gzip module for Apache does. (I've toyed with making a svg-gzip serializer for Cocoon2, but at some point after the beta phase, it broke and I think the mod_gzip approach is a good one.)