I wonder how heavily the script was rewritten from what may have been offered to Shatner (though has that ever been formally confirmed?). If it was just a case of name substitution you'd have to wonder how they'd thought they'd get him to do a story that would have painted his character in a fairly bad light considering the famous ego.
Mind, getting him on board might not have been helped by it not being a very good script. And the old age make up didn't look very good to me in SD, so it's probably unfair to blame the Blu Rays for how bad it looks now.