No matter what you put in the newsgroup charter, moderators effectively control the newsgroups they moderate, and no one's going to take the newsgroup away from them unless they do something egregious. And even then, it will be months of fighting over it. If you don't trust the moderators, don't vote for the newsgroup, no matter how good it sounds. No matter what the moderation criteria for the newsgroup, even if it's just strict robomoderation against crossposts, sooner or later you're going to want to post something that the moderators are going to reject. You might be able to talk them around, but you're probably going to just have to swallow your rejections and put up with it.
Moderators reject posts.
That's the whole point of a moderated group. Don't think it's never going to be you too. If you have anything else to add to this post, or any suggestions about it, don't hesitate to mail me. Thanks to Gary Johnson for his encouragement and to Tim Ottinger for the initial framework of this post. Thanks also to many news.groups readers for suggestions and feedback.