Make a rule that limits posting from new/low-community-karma accounts when a post flair is enabled?

Hey all - a community I mod is toying with the idea of having some way to soft-lockdown a post if it is getting out of hand. Rather than lock it for everyone, we were thinking we could have it auto-filter or remove comments that had less than a threshold for community karma. The problem is that we, of course, don't know which posts will need this treatment in advance, so it needs to be tied to something we can activate. I was thinking we could have a special post flair that would cause this (IE "Limited Post" flair), but all the advice I could find was that automod checks post flair when it is created, but doesn't update if the flair is changed, so activating it this way wouldn't work.

If this is possible somehow, could somebody give me some advice on how to get it to work? This is all I've been able to find on it so far, but if somebody has a better way, I'd love to hear it:

--- type: any author: combined_subreddit_karma: "< 50" flair_template_id: "Post flair here" action: filter action_reason: "low karma message on restricted post" comment: | "Your comment has been removed due to not meeting subreddit requirements." ---