Interesting idea. Not sure what Google would think on that, but I believe 1 of 2 things would happen:
1) Google spiders your backlinks and comes to an error page when following to your unregistered domain and doesn't count any of your links.
2) Google spiders your spammed backlinks, but because your domain is not yet registered, you don't get blacklisted or banned. Google counts all the backlinks and, when you do register, you find your domain indexed and setting in a nice place in the SERPs.