Hey there! Unfortunately there is not an easy way to do that inside cPanel. cPanel specifically programs the existing proxy subdomains of cpanel, whm, webmail, autoconfig, autodiscover, cpcalendars, cpcontacts, and webdisk directly into the Apache and DNS configurations. In order to change this, you would need to make manual configuration changes to the Apache template system, and also adjust the DNS templates so those zone get created automatically.
While I don't have specific instructions for that work, documentation on Apache templates can be found here:
A custom template file modifies how cPanel & WHM builds the Apache configuration's virtualhost entries.
docs.cpanel.net
and I'd recommend performing this work on a test system with no live accounts first to ensure you get the configuration working how you expect.