[black_eagle]

Kodi does support multiple releases of the same album for music that has tracks in individual files that are tagged with Musicbrainz ids, using the mbids to identify different releases. Cue sheets do not offer mbid support, as I have said before it is limited compared to tagging.

May I just add this mbid tag to a file which contains the complete album? I suppose that as that specific mbid represents the specific release it should be the same in every song-file that belongs to that release.

Or am I just simplifying the situation to suit my needs? ) 

Yes, the 'MusicBrainz Release Id' is consistent across every track of a specific release, so that each track can be tied to a specific release.

Gotta ask, why don't you just tag the actual files, rather than sticking with cue sheets ?  Ultimately, it's easier and tidier than a cue sheet, Kodi understands pretty much most of the tags and produces better results when using them.  There is software available that will tag all your stuff correctly with little user intervention, although it's possible to select different versions of the same album manually in the event that it isn't identified correctly.