I've spent the whole day working on getting a more flexible and successful build system for eXist. This is what I've added to Greg's script:

• It now checks for the presence of Saxon and warns if it's not available.
• It checks for three XSLT files, and in each case, if the file is there, it transforms a target file in the build tree. These are for conf.xml.tmpl, mime-types.xml.tmpl, and controller-config.xml. This should allow us to set up build environments for each of our specific projects.
• It excludes XML Calabash and includes FOP. The former was blocking the build because its download location is down.

Found a number of problems with eXist, which I've reported, including a bad one once the webapp is running: you can no longer call transform:transform with a relative path to the XSLT file, otherwise you get an error. A full path from /db seems to work.