Daily Post Limit
Perhaps better than limiting users to 4 post per day, instead install a mechanism whereby a poster can flag a post to be 'monetized. When monetized posts are upvoted then the crypto awards are applied. If not then only the rep rewards are assigned. Users could then monetize a maximum amount of posts per day (eg. 4) and any additional posts would not be rewarded with steem but only in reputatiom rewards.
Good point, thanks for your comment