The problem with this is if we open publicly and have such instant payment, you know some people would make accounts up to minimum requirements, posting bad quality posts, then bot spamming hundreds of posts with randomly generated after joining campaign, right before a CRON, to then immediately withdraw.
Then in order to alleviate this from happening only allow hero and legendary members to join, while keeping the current senior members in the camp.
To do away from the potential spam issue put in place a rule if there were over 25 posts a day then your account would be given a warning then if it continues they would be kicked out of the campaign.
Immediate withdrawals are possible such as with the one I am with now. They bank the credits then allow withdrawals which have been immediately sent to my payment address that I choose to send too.
So these requests are quite possible you just need a certain amount of time to implement them.