ayrton, since you're chiding everything on this thread, I assume that you've read the links that winnie provided? Then by now you understand that the cabinet is not part of the panel. The cabinet is the "cabinet", and the panel is the "panelboard", which needs of course to be mounted in a cabinet.
I haven't seen anyone here suggest modifying a panel; they have only suggested mounting an unmodified, new panel into an existing cabinet.
No problem there.
And if you're still queasy about that, follow winnie's links, and the links in MikeHoltForum threads that winnie linked to, to find UL Listed retrofit panels (or panel interiors if you prefer) in Cutler Hammer's CH, BR, and PRL1a lines that are listed to be retrofitted into any cabinet of suitable size.
