I interpreted this case as
- the default position is posts are not Moderated. This is not the result of a promotion. All members get this, normally.
- exceptionally, some users require to be Moderated; demoted temporarily if you like.
Since there isn't a "revoke" option on User Group permissions, that leaves only Never. Hence my suggestion.
The only way I can see to NOT use Never is to have the default user (Registered) as "Moderated" but promote them all immediately by default to a secondary group where "Follow Moderation Rules" is set to Allow.
And then DEMOTE (remove secondary group) those who are being watched. And PROMOTE them again when the watch is lifted.
Without going into it further, I'm not sure how you'd create a setup whereby members were instantly promoted (added to a 2ndry group) on registration, BUT not ever automatically added back to it if they were manually removed/demoted.
Which brings me right back around to my original suggestion.