If using domain and title custom fields in whmcs provisioning plugin, can the site that is created,

I know that, at site creation, you can not have the custom fields ticked or the domain mapping plugin will not work right.

Having said that, if a site is already set up with a custom domain and/or other custom fields, can your plugin work to convert a "mydomain.multisite.com" to a "mydomain.com" on a site already configured in multisite.

I would like to allow the customer to be able to create a custom domain name at site setup for the free trial site, then later have the option to upgrade. Obviously, this would require a domain name already set up and I'm sure the default one would not be what they want.