Eventually figured out that I had a corrupted exist-jars.xml file; after starting again from scratch, I got eXist and Cocoon to build. Then I followed these instructions to add Saxon (using the single-file SaxonHE release) and my own two jars, and to set up utf-8 handling. After that, Cocoon seemed to be running fine, but eXist is still MIA. Another note from WM instructed me to copy the ws-commons-util-1.0.2.jar from EXIST_HOME/lib/core into the generated COCOON/build/webapp/WEB-INF/lib. After doing that, I was able to get to the eXist admin web page, and create a collection; but the jars are still unsigned, so the webstart client won't run (although that also fails on a sitemap error before the signing error even happens), and trying to connect from a local admin client also fails. So nothing is usable yet.

I need to figure out how to sign the jars -- I think this requires a key, which I don't have, and I don't know what kind of key it is, or how to get one or generate one. If I can do that, then an alternative approach is available: I could use the repackaging strategy on eXist 1.2 with Cocoon 2.1.11, to get a working system with eXist 1.2. This would at least be a big step forward. 1.4 could wait on WM having the time to finish it.