I don't think you can really have good moderation of a stable group without the moderators being members of the group themselves -- and known and trusted/viewed

I don't think you can really have good moderation of a stable group without the moderators being members of the group themselves -- and known and trusted/viewed positively by a majority. Otherwise they'll just be perceived as jerk outsiders who swoop in to make more trouble than they solve. And they will face constant pushback and non-compliance.