@ltyl I think that you could use a proxy that would set the X-Forwarded-For: header to a known bogus value. If you put that in front of FusionAuth, it should happily set every ip address to that value.
https://fusionauth.io/docs/v1/tech/admin-guide/proxy-setup#headers-to-set
This will mean that you can't use IP based access control lists, however.