Music database identifier (e.g. MBID) in EAC FLAC/Vorbis metadata

Question

I want to …

• … rip Audio CDs with FLAC output using Exact Audio Copy (EAC).
• … include an universally unique identifier for the exact release (specific label/year/country/etc.), additionally to common fields like artist, etc.
• … preferably use the MBID (MusicBrainz Identifier) for this cause, since MusicBrainz is free and quite complete.
• … add it via command line options, as EAC tags work: -T⠀"VORBISCOMMENTFIELD=%eacplaceholder%"
• … have this done on-the-fly during a single rip (i.e. no manual post-encoding lookup).

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My problems are that …

• … the EAC FAQ lists some placeholders, but merely %cddbid% (freedb ID) in regards to this question.
• … I can’t quite find standardized Vorbis comment fields corresponding to music database identifiers (like CATALOGID/CATALOGNUMBER or concrete CDDB/freedb/etc. IDs).
• … though MusicBrainz Picard maps their tag system rather nicely …
• … EAC seems to be the limiting factor, since it seemingly cannot convey fetched metadata arbitrarily to the encoder parameters.

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Does somebody know a solution to this?

Or is this too specific and ought to be asked someplace particularly devoted to EAC?