I've just filed a PR  for pulling the container element validation
proposal into the actual spec chapter.
Some smaller details are still missing (metadata API extension as per
the pending API PR, more examples), but it should be good for review
overall. Could you let me know of your thoughts by Friday, please? In
terms of actual contents, nothing dramatical has changed compared to
the appendix, I've mostly improved wording, clarified details etc.
In the light of today's discussion this doesn't contain container
element validation for arrays. I'm not super happy about omitting it,
but it feels safer to leave that one for another time (and we could
still add it back during the public review, should we find a
satisfying solution and feel very confident about it).
Once that one is merged, I'll prepare the Public Draft over the
weekend, it should be up for review next week then. I'll post the
original appendix to the proposals page on beanvalidation.org
Looking forward to any feedback,