One way of doing it... You can blast away the original markings / copper using laser and put something in place like sheet of copper or something that resembles copper, add solder mask layer on top. Done.

These operations are not hobbyist level, they have access to the machinery to make it trivial.

Please, I could just fill the gap with the same-colored solder mask, flatten it out, cure it, you'd never see the rework.

It is so trivial anyone that's ever done fingernail polish can do it. The process is roughly the same.