Comment 9 for bug 1748132

Another way to save public IP addresses is to use subnet service types, https://docs.openstack.org/ocata/networking-guide/config-service-subnets.html - using that you would have multiple subnets on the external network, but some can only be used for certain types of ports. That way a floating IP subnet could use global addresses, but a router gateways could use private addresses. That way it is still possible to verify reachability of each router since it has an IP, which would not be possible with this proposed change.

Have you tried using this existing extension to see if it can meet your needs? If it doesn't then it should be possible to approve this change as long as it doesn't change the default behavior.