This ticket has been in process for nearly two years, and was finally resolved at the last Council FTF meeting; I developed an implementation plan on the wiki, which Council commented on, and this morning I implemented the changes according to the plan. Checked everything in the resulting Jenkins build, and made a couple of tweaks to an example. All seems to be well. if so, and if the resulting schemas do what we want them to, we can adopt this in MoEML and elsewhere following the next TEI release.