I am sorry to learn that my reply on the Tower/RA harquebus has not been able to satisfy your thirst for knowledge. I cannot explain for the sliced in pieces of wood any better, though. Blaming it on possibble recoil damages does not make much sense, I, too, am afraid.
You are definitely right in attributing tubular back sights mostly to target shooting; I have seen such oversized sights placed on matchlock, wheel-lock, and flintlock guns apparantly re-used for target shooting. Of course, these are mostly 19th century crude alterations.
I also agree that the use of replaceable aperture blade sights was the anticipation of a very modern feature long ago. The only reason I can think of why that idea was dropped for centuries is that the guns of those time periods just did not hit well enough to catch up with the exactly cut aperture sights.
You are, in my opinion, also right in commenting on the two staked punches on top of the back sight in order to hold the aperture in place. Of course, it was no longer easliy interchangeable after the staking.
Thank you for paying such detailed attention to my posts, my friend!
All the best,