FYI: I ended up submitting this as a paid support request. I am probably not allowed to give you the full response from eZ systems, but the bottom line was:
"Unfortunately you are very right in your analysis of this issue, and there is currently (to my knowlege) no simpler solution to this."
Thanks for the candor eZ systems. Unfortunately, this is a feature we require on most of our websites. Being able to (easily) manage many different kinds of metadata for our content objects, and allow our users to find objects in many different ways using this metadata, is something we try to focus on.
