Using this methodology does seem to work, i.e.
sudo ifconfig lo0 alias 172.16.123.1
docker run -it --rm busybox ping 172.16.123.1
or with hostname mapping for app config convenience
docker run -it --rm --add-host=docker.local:172.16.123.1 busybox ping docker.local
But again… this is a manual process, making it a barrier to entry/adoption
If you’re concerned with coming up with non-conflicting IP schemes, then just make this an option in the settings panel. Give us a textbox to enter any IPv4 address into and automatically manage the lo0 alias on OS X.
This at least gives teams a consistent way to operate via a intuitive interface