I can live with it as-is, but I guess I'm still stuck on the purpose of having docker feel native on OS X/Windows
I understand the programmer-centric thinking of all things same on all platforms, but let's be realistic here, you're doing docker native for OS X/Windows so developers can better seamlessly integrate docker into their everyday development workflows, which I applaud because I've been doing this manually VM's since the early versions of docker with various hacks to get port's and such exposed out to the host (OS X) etc.
I can't imagine that even a stretch goal here is to ever expect people to run containers via docker native for real-world production usage. With that in mind, then what's the harm in making something easier to use for developers. I'm not suggesting a docker cli UX change, we're just talking about making some well-known IP (maybe off by default, and configurable in the docker native settings) that's always-on that can be routed to from the docker containers, and this lives solely in the realm of the docker native VM and supporting application that manages it.
If your goal is to make the Linux VM invisible, then your "host running containers" is OS X, not Linux, and without the above there's an obvious hurdle to making this a seamless integration into your development flow?
Here's the scenario I envision:
Hey new guy, we all develop using docker native to support our apps, we run a custom nginx for authentication which must proxy all your apps, but we let you develop/run your apps from your native IDE. Go install docker native, and pull the latest custom nginx and set it up to proxy to the port you pick in your properties. Oh? What IP do you proxy to? Well that depends, every time you switch networks between office/home/vpn or get a new DHCP address you're going to have to figure out your IP and go and re-configure your proxy, because, there's no reasonable way for us to pre-configure things to "just work" for you. By the way you have to be online so your network interfaces are up.
Is this an elaborate example? Yes... but it's one that's already true for me, and I can easily envision lots of scenarios where you need containers to reach out to things running natively on your "host" (OS X, not Linux)
Again... I can live with this, I just think you're missing an opportunity to make things easier on developers