Is it possible to put a site other than #1 as a Multisite top-level domain?

Question

Assuming a WordPress network with subdomains:

[blog ID #1] http://mysite.com 
[blog ID #2] http://site1.mysite.com 
[blog ID #3] http://site2.mysite.com

Is it possible to move one of the subsites to the home site URL? Result:

[blog ID #1] (inaccessible or I don't care)
[blog ID #2] http://mysite.com
[blog ID #3] http://site2.mysite.com

I realize that there's no simple configuration change, and that URLs are often hard-coded in the database, so it's not an easy task.

But I'm wondering if this is possible at all with "Sunrise" site mapping, some plugin, etc? Another acceptable result would be:

[blog ID #1] http://mysite.com
[blog ID #2] http://mynewsite.com
[blog ID #3] http://site2.mynewsite.com
[all further blogs on mynewsite.com as well]

ie. all subsites should map to the new domain

Community · Accepted Answer · 2017-04-13 12:37:38Z

I've never changed the main site URL (scenario 1), but I know it's possible: three relevant links found in a quick search.

For the second scenario, although not optimal, the standard procedure applies:

install the plugin WordPress MU Domain Mapping
park the TLD mynewsite.com in your Control Panel and point it to the folder of the main site
create a sub-site new.mysite.com in the Network and use the plugin to map the domain mynewsite.com to it
enable wildcard subdomains for mynewsite.com in Control Panel
create a sub-site new2.mysite.com and map the sub-domain site2.mynewsite.com to it

All the mapping process is well explained in the following tutorials:

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