The only problem with that, at least from my view, is professionalism.
Granted, I/we aren't exactly the best example of professionals, but I'd hate to send everybody to 'purgatory' just because of a few spammers.
This is also highly dependent on me. Sometimes I can be here 24/7, other times I can't...so I'd hate to put somebody totally on hold [that could potentially be a paying member or active poster] because I couldn't be here for a few hours.
Right now, they can instantly post 3 posts as soon as they at least verify their account.
Sending them straight to purgatory, while fun sounding, might shun some people away, don't you think?
I don't mind doing something off the wall, but not so sure about purgatory...keep them wheels spinning Koi, you good at this stuff !