Before you go out and get a punch for this, I'd consider farming this out. I've dealt with two companies _capable_ of doing this sort of work, and can recommend them on general quality, however I have not used them for electrical panels, and cannot comment on the specifics of their work on such projects.
The first is 'Laser Laminations'. I've used them to precision cut custom motor laminations for some of our prototypes. You send them a '.dxf' drawing of what you want, and get it about a week later as holes in metal. http://www.laserlaminations.com/products.htm
The second is 'Hales Engineering' in Camarillo, CA. They do general machine building and welding, and I've seen them make custom electrical equipment enclosures.