The box would have to be metal, and that would still have to be machined somehow. We do our best to offer kits that can be built by someone living in an apartment (or even a dorm room), and requiring metal machining is a little beyond what a lot of people want to do and making one mistake in this process can lead to having to start over.
On a higher level, if someone wants to buy one of our kits but also wants to change out all of the parts for something else, that is a substantial investment in time on our end to try to support something we've never tested nor listened to, and sometimes it puts us in the awkward position of trying to tell someone that some of the fancy parts they want are a downgrade from what we provide.
