In this order:
-IDs and forced anon everywhere, sage visible.
-Raise the timers everywhere and implement a system that detects sudden spikes in activity and either raises the timer or disables posts/thread creation for a set time.
-Longer bans: 1 day ban becomes 3 days, 3 days ban becomes a week, week ban becomes a month, and so on.
-Enforce rule 6.
-Autoban for spam/buzzwords (reddit, discord, tranny, sneed, etc) and catchphrases, and an algorithm that identifies and instabans wojaks and frogs.
-Change the captcha system to something more bot-resistant.
-Way more rangebans to stop the schizos, spammers and pedos. Possibly a "pseudo pass" system for "innocents": if someone is caught in a rangeban but claims to not be the offender, he can request a "pseudo pass" via a form on the site that requires an email and that the request be sent from within the banned IP range. This "pseudo pass" would allow to post despite the range ban (but captcha stays), and can be revoked any time by mods should a user abuse it.
-More and harsher moderation to weed out indesiderables, starting from the smaller boards, then the more active ones (plenty of rangebans and anti-flood system should already help)
-Remove rule 15 to spite Barneyfag.
-Nazimoderation on the top boards: /pol/ outside of /pol/ is a bannable offence, deleted spam threads give all those who posted in it a ban regardless of what they posted.
-/cel/ - "Celebrities and Gossip" board for the kpop, idols, ecelebs, youtubers and actor shitpost containment, with nazimoderation.
-Disable thread creation on /trash/, cartoons go back to /co/, possibly make an unlisted /fur/ - "Furshit" containment board and moderate it with an iron fist (irl pics banned, fursuit sex banned, basically make it /aco/ but for furniggers).
-Seizure-inducing css on /pol/, with random blanking of posts, random embeded files, and other fun features to make it unusable.
-/civ/ - "Civics" once /pol/ is gone.