The nice things about the Federated universe is that, yes, you can bulk create user accounts on your own instance - and that server can then be defederated by other servers when it becomes obvious that it's going to create problems.

It's not a perfect fix and as this post demonstrated, is only really effective after a problem has been identified. At least in terms of vote manipulation from across servers, it could act if it, say, detects that 99% of new upvotes are coming from a server created yesterday with 1 post, it could at least flag it for a human to review.