Some campaign managers have taken the initiative to make minimum Merit requirements compulsory to join their campaigns but those managers were already the ones with high standards. They were not the problem, it has always been the managers that just blindly accept the first x hundred people to apply and pay them regardless of the spam they produce.
Honestly, I think it is a good practice.
But I think signature campaigns should not be restricted for non-merit heroes-legends members, their stacks should be reduced in a half, I think it will be fair and enough to stimulate make quality posts. And will give more income for merit members. Fortunately , there are managers who already implemented such practice.