50 posts within 7 days might lead to spamming across the forum; you must need to reconsider it.
Why?
Don't we have campaign which allow you to post up to 55 a week for individuals? I do not see anything wrong here if users agree to make whatever post they have asked for.
Yes we do have Bitvest and 777 where the maximum that you can post is 60 posts but you are not required to reach that number, I have seen participants reaching that number and some of their posts are good, and I've seen participants not only on these two campaigns who have only required to posts 15 posts per week yet their posts are classified as spam.
When it comes to posting requirements let participants decide if they can keep up with the number without spamming the forum, it's joining at your own risk.