Anti-Splog Move wp-signup.php

I have a question related to the Anti-Splog plugin. The Anti-Splog plugin catches most of the splog signups, but they're still sitting there where I have to do something with them, which I don't want to deal with if I can help it. (By the way, it would be nice to have an auto-delete option.) So for now I've checked the option to move the wp-signup.php page daily. That put a stop to the splog signups but that creates another challenge. I want to link to the signup page from an external site, so it seems like using the ust_wpsignup_url(); function wouldn't really work, right? Is there a manageable way to handle linking to the signup page from an external site?

If it helps, I'm using Pro Sites and I don't want to have a free level, only paid. So if there is some way to just disable the free signups and only allow paid signups, that would be perfect (and no username-only signups either). Then I could just leave the signup page alone rather than moving it, which would make linking to it easy.