I haven't come across this exact issue in the forums yet. I'm moving a WP Multisite from a virtual host to a dedicate host. I did a fresh install of WP on the new server with a temporary URL (http://website2.com). The old WP site (http://website.com) will be archived. Is it better to activate and set up the multisite network on the new server under the temporary domain name first before transferring the original domain name or transferring the domain name then activating the multisite network? The one caveat is that the old site will need to remain active while the new site is set up.
Your help is greatly appreciated.