The Specialized pedals would make it a lot easier. You may be able to buy some aluminum flat bar stock that is 1 cm taller than the existing plates, let's say something like .1" x 1.0". If so, you could simply cut to length, drill and countersink holes, and bolt them on. You'd probably want to screw some material to the outer part of the quill/platform on those to bring it up to the same level. Pretty easy. I'd use delrin...

For the metal, I'd suggest you use 6061 or similar at full T6, and don't bother with annealing or heat treatment. Not necessary.

Campy pedals would be much more involved. You'd need take a pattern from the existing cages by tracing onto paper, modifying it to the new higher pattern, cut out the pieces, bend them, and then do any finishing work as needed. I'm not sure but I think those rivets are peened over extensions of the pedal chassis itself. You'd probably have to drill them out, and then drill and tap the pedal bodies to take screws. Like I said, more complicated.

FWIW my Campy pedals are made from .10" thick aluminum. You can buy this from various online retailers.

How difficult this project would be is entirely relative to your experience level. Also, what tools do you own? Have you done any aluminum fabrication? any metal working experience? If not, how about woodworking? If you commit I'm sure that there are plenty of forum members that could help you with any specific steps.

Main thing is to wear eye and ear protection, and don't ever try to cut or drill metal that isn't clamped down. And watch your fingers!!!!!