Spending a lot of time managing additions and rollouts for customers, IMHO, often the best way to do this is to simply add pages that are exposed only to roles that  are part of the production process so they can see all the new functions, and then , when its ready for go live just check the "all users" permission. I think its a hassle to create multiple sites and backup and restore all day... just use DNN the way it was intended and do the new stuff behind a hidden page...or hidden module.  In fact you can even do that at the page level..hide the new module on the public page until its ready for release. 

I addition to add to the sql script could be to also change the name of the SMTP server to a non existing one to avoid accidental emails escaping when testing.