Allowing people to select the blacklists they want is part of the change we're making.
We have to make some kind of change anyways, because current usage of blacklists slows down Hivemind too much. As we need to make a change for performance reaons anyways, it looks like a good time to also make this improvement, since it's relatively easy to do.
Edit: I just realized your suggestion was slightly different, you're suggest allowing a user to make a whitelist to reverse blacklisting. We could do that also, but I don't think it's necessary, since blacklisting just provides extra information that a user can ignore anyways. It is not a muting function.