If you think you can cut arbitrary shaped holes in large sheet metal
boxes with a milling machine, you have skills I do not have.

Not planning on large sheets anyway. But thanks for your comments,
they're helping me abandon overly expensive possibilities.

I'm thinking my best niche would be to custom mill boxes up to 2X2X1
with walls at least 1/4 inch thick, with top panel either 1/4 or 1/8
plate up to 2X2. That's plenty for QRP, subsystems, microcontroller
boxes, and some scientific apps.

The Eternal Squire