Well, clearly the hope was that Ash as a conflicted individual with human memories and loyalties and longings would be more engaging for the audience than Arne Darvin II. Could have been.
The ridiculous Frankensteinian poohbah about how the trick was accomplished is what's wrong here, not the character premise - "Manchurian Candidate" may be an oldie, but it still works.
Yeah, but they could have done all of that even with the augment virus, since most of that was having Ash Tyler's memories implanted on top of Voq's.
I agree the ghoulish surgery was completely unneeded.