That would be a lot of tricky work, for sure.
As far as countersinking the screw holes, I have made a dimpling die to form most of the countersink
when making thin iron mounts for muzzleloaders. Such a tool leaves much more material around the screw head. The countersink is then cleaned up a little with a countersink cutter. I don't know if distortion would be a problem with the large rounded plates, or not.
The tool I use is very similar to one used for the installation of flush rivets in aircraft skins.