Domain name in setup of autoprovisioning as call server address

It would be a very powerful feature if the spbx gave the option to use an FQDN as the call server address instead of just the LAN address.  It seems the SPBX only uses the LAN IP address as the call server address when creating a config file in autprovisioning.  If it allowed us to enter a domain name to be entered to be used in place of the LAN 1 address, then the customer could use a split DNS and the phone could be moved from on premises to off premises easily.  Now a phone that is provisioned on site cannot be taken off site easily because it needs to be reprovisioned. This would help sell more on site systems to be able to offer this feature.