Installer should detect that IPA server is being installed on public network (address block outside RFC1918 or non-link-local IPv6 address) and scream loudly that admin should harden server configuration.
Not doing so will:
etc.
Some recommendations are captured at: https://www.redhat.com/archives/freeipa-users/2014-April/msg00243.html
Metadata Update from @pspacek: - Issue assigned to someone - Issue set to the milestone: Future Releases