The only caveat I can think of is that--except for the PR that protects XLIFF-defined elements--you have to expect its support to be as for an extension rather than a module.
Exactly, that's what I also said in the meeting ;-) [but we had a bad feedback between myself and Ryan, so it might have broken up]
I guess, Ryan, and others might benefit from allowing the mda explicitly in Glossary.
On the other hand, if Ryan and MSFT are just looking into a way to include metadata in the glossary module w/o defining their own namespace for it, the mda is as good as any other namespace.
The question is I guess, if MSFT expect a third party to process and roundtrip the mda based metadata that they put in the glossary module.
It's probably worth looking at the detailed use case to tell if the mda is in need of module handling rather than extension handling at the Glossary extension points..
Anyways, using mda to completely replace gls violates the high level PR saying that user defined extensibility, no matter if mda or custom namespace based, must not be used instead of a core or module feature.
Dr. David Filip
OASIS XLIFF TC Secretary, Editor, and Liaison Officer