Yes, it is possible. This is the feature I wrote during the last days for the pro version of Multilingual Press.
One problem is that wp_upload_dir() does not always return the correct values after calling switch_to_blog(), that makes attachment copies unnecessary difficult. Besides that most things are simple. TRUNCATE the new blog’s tables and replace them with the content of the source blog, then update the values which are different.
Things get tricky when you need new relationships between some selected blogs, but all that is not special for the root site.