Ok, I'm having some slight issues. I was able to do drmike's method and it works perfectly. Here are the snags I'm running into:
1. When I delete a page from one of the parked domain sites, it doesn't stay deleted. Like it looks like it deletes fine, but when I refresh, it reappears. I'm deleting from the Manage area
2. When a user, who has cross permissions on the main site and also one of the parked domain sites, the user has to relogin in if they were logged to the main site and try to access the parked domain. (I'm thinking this might be a cookie issue or something similar because for the parked domain thing to work, I have to go to the database and under wp_blogs change the site_id to match the blog_id. Wondering if there is a way around this?)
3. With a new parked domain with it's own blog_id and same site_id, I can't create a subdomain off the parked domain. I get a redirect to the main Mu install trying to create it under the main Mu install rather than under the parked domain.
Other than that, this is great! Thanks drmike!