The one critical flaw that has still not been addressed is......scope mounting.

Look at the eye relief on that scope and tell me if you think that looks correct. While the externally thread breach plug sounds like a good idea, its a nightmare for mounting a scope properly. The ocular bell on that scope in lined up with the trigger. How many scopes do you think have over 5" of eye relief?

Sure this can be solved with a base that over hangs the breach plug cap but then the cap becomes more difficult to remove.

Assuming that eye relief is fixed lets look at scope height. How much lower can you go before the ocular bell gets too close to the action lever?

On top of all that it is still butt ugly with poor fitting stocks.