@Alexander-Dukhno, thanks for the continued work on this!  But, no, I would completely remove any dependency to o.h.metamodel.  We'll run into issues simply by using MetadataSources, period.

In my opinion, I'd probably completely revert 922a8d5 & c820864 (or hard reset to 48a3014 and force push).  Was there a particular issue you were trying to mitigate by switching to metamodel?