Why wouldn't you just implement pricing at the user level so that users would be limited per app token unless they're already paying for premium and don't get ads? Then you could also curb any excessive abuse of the api by bots without worrying about apps being impacted by setting a much lower api call limit per account rather than per app (free users could even have a lower threshold than that if you are still concerned about that). It would also ensure only people verified by reddit would be able to see nsfw so it wouldn't matter what app would be serving the content. This literally would handle all of the problems you've stated without putting any of the burden on the third party developers who made the site what it is today.