I'm not stoked on having two pieces of metal hardware connecting like that at the dinghy. You would need to be sure they can't get caught at a bad metal to metal angle that puts them in a compromised weak position. Be wary of side loading, etc. Plus pinch points for fingers.
I like Peter's diagram or anything that avoids metal hardware at the handles.
I bought the Wichard SP400 two years ago (only $294.98 at the time!) because I was in a bit of a time crunch and like it. Much better than stainless cable I previously had.
As you said though, most of the value of that strap is the shackles... and the fact it is pre made and you can order it off the shelf.
That said, most options will work fine and you'll probably change your mind after trying your first pick anyway if you are like me. And then proceed to live with it for at least 5 years anyway because it is just fine.
I am curious if the front handles being relatively far aft will pose any balance challenges, as that is the other piece of the puzzle... getting all the pieces the right length. That is the step buying the adjustable Wichard step let me sidestep.
You may well have already seen it, but there are a few comments in
https://www.facebook.com/groups/159221667846990/permalink/1269698543465958/ around reinforcing the handles. I'd have less concern just lifting it to set it on deck vs having it permanently hanging off the stern.