There should be a place (places due to RC vs. watchlist issue) on the backend where you can configure:
* What filters there are
* Whether they are available on new RC page, or both old and new.
* The default value (may be based on a preference, can vary by watchlist vs. RC, e.g. 'hideminor' vs. 'watchlisthideminor' preferences) (the default can vary for non-preference cases too)
* The actual modification this makes to the DB query
* Prioritization (where it appears in the filter list)
* Tags (when rendering lines, needs to check what classes to tag it with, e.g. "Experienced", "Your edits", "Completed review").
This needs to extensible by extensions (we already have a need for this, e.g. ORES, Wikidata, Translate).
I suggest hooks would be a good option for extensibility, but @mooeypoo points out having extensions modify a wg could work.