Sorry no, it would need the pool to be literally taken down and manually edit its database before restarting it. It simply doesn't have that kind of functionality. Given the fee free nature of the pool I'm reluctant to add code for such a feature.
What if someone lost control of their mining address' private key?
Edit: It just occurred to me that if someone lost control of their mining address' private key, they wouldn't be able to sign a message with it to prove that it belonged to them. Still, I'm curious to know how such an issue could be resolved here; it wouldn't be ideal to have someone's subsequent payouts sent to a black hole or a thief.