Usually the campaign manager will edit the title to [Open/CFNP/Closed] which itself enough to identify the status of the campaign at any moment. But there are some exceptions like even if there is no slot left still manager would like to hire highly recognised member of the forum which may be available in the first post of the topic generally but the proposed idea is also good but not really necessary though cause if someone isn't reading the requirements before posting theit application then they are not fit to take a slot.