Wow, yikes. Sorry for the double post. I did search around before posting but I definitely missed this. Happy to remove it.
Perhaps one nuanced difference is that I’d also like to see this work for a badge that is granted manually, say by a moderator, instead of automatically via badge queries. For example, we have a “feedback” badge that moderators can give out for really thoughtful posts; I’d love for this badge to “unlock” a flair badge (by adding them to a group). It seems like your approach (adding a mirror group) would cover this case as well. Though, the post focuses mostly on SQL triggered badges, so I thought it was worth mentioning.