I just skimmed it but my first impression is ... well, my first impression is that it's very nice to see a well-written design proposal, actually! Looks good.
Currently OpenACS 4 makes very little use of ns_xml, in the core just to parse query files and to parse package .info files. It's not used to generate .info files, nor is the XML doc tree retained after a .info file is parsed.
Obviously we're going to be making much heavier use of it in the future, especially in client packages. So having someone pick this up, improve it and perhaps continue to maintain it for some time, at least ... yeah, it's great.
