Why not simply fill the cupped rod end with metal set epoxy, level it off, and move on.
Some deformation of the bullet nose has no effect.
You shouldn’t be pounding on the bullet when seating it anyway.
Muzzleloading rifles are short to medium range tools to begin with. Even if your modifications have any effect, it will be very small and immaterial for what they are meant to do. A gun that will only group it’s bullets in a 3 or 4 inch group at 100 yards will still make a killing shot out to 150 yards if properly aimed.
For fairly serious paper target competition, there are many other variables more import at than bullet nose condition.
Sorry to pop your balloon.
BTW, your technical drawings are first-rate.