Like Wilba said, when I first asked him to help me with an Alps-compatible TKL PCB, he explained to me that when designing a new PCB, it makes sense to design the case around it, rather than trying to design around existing products. That's because I originally wanted the case to be compatible with Phantom PCBs.
I still think making a milled case for the Phantom is a worthy goal, since no one has really provided a great case for it yet. It doesn't have to be open source, though, since it wouldn't really make financial sense for individuals to have one-offs produced.
The problem with open sourcing hardware designs like that is that as someone who makes things, it can be discouraging to see others selling your designs for profit (e.g. Chinese taobao sellers), when the intent was to make it available for everyone to use.