I'd soft solder the new sight to the current base already on the bbl if you don't want to take the base off of the bbl.
Large, flat surfaces,,tin them properly and they won't come apart. Many modern guns have sights and even scope bases attached with soft solder.
No holes, done right no discoloration to the metal as the heat is only in the 350/400 range.
As far as the peep sight itself,,there are some Military centerfire bolt action rifles with a peep in a flip up sliding vernier out on the open rear sight. They work OK, though never as sharp an image as the one right in front of your eyeball.
It takes a larger hole in the peep than if it was close up to your eye.
It really helps to have a deep cup hole to shade the aperture when it's that far away from your eye.
Some of the Military ones simply cross hatch lined the face of the flat surface the peep hole is on.
It's not enough to cut the glare if the light is hitting it right and you'll have a problem seeing the front sight through it.
Give it a try. If it doesn't work,,warm it back up with the propane torch, take it off,,try something else.