Here's what I've come up with: Allow owners to define new archiveSounds a lot like my proposed enhancement to the filter funnel already present in the Topics/Messages lists. Right now it only has a Date selector, but it could also have selectors for topics with or without specific hashtags. I don't see why this wouldn't be a filter ability for any member, not just an owner.
A column of hashtags with two checkboxes each (contains, does not contain), similar to the new one for the bulk feature could do the trick.
This could be a step on the way to my wish for the ability to filter and sort by any message metadata.
Now if the proposal is that the owner (moderator?) be able to create and name specific filter presets that members could choose from that would be cool too.
Two obvious presets (not defined by the owner) that ought to be included are "Followed" and "Not Followed". This would at last bring that functionality to the group level. And then we can rebuild the home page (messages from all groups) in this model, for greater consistency and clarity. But I'm getting ahead of the game.