Nice summary, thank you for taking the time to critique and compliment.
The newer style, I believe the thing that is going to give you fits the fastest is the scarifier bar.
You're probably just as far ahead to make your own and make it adjustable
One other upgrade to consider.
If using blade to contour ground, placing weight to one end will allow that edge to cut in faster.
If that is a use for this attachment, a pivot on the hitch may be useful.
If I was your ever going to do is flat, then it would be completely unnecessary.