Shatners idea was awful. He comes up with crazy stuff to bring his character back. He must have really regretted Generations.
He's his own worst enemy. He should just accept the decision he made. He took part in the first TNG movie, ultimately agreeing to a death without Bones or Spock around to see it.
Fast-forward 10 years later, to the current producer of Star Trek asking him to take part in a storyline, that brought him back. But not as Kirk. It would've been fine. Still would. On Enterprise OR in the Abramsverse. The fact it's Shatner would be enough of a knowing wink to the audience. Bill is also not simply Kirk. He's changed over the years. He's T.J. Hooker. He's Denny Crane on Boston Legal. He's the Big Giant Head on Third Rock from the Sun. He's the Dad in $#*! My Dad Says. I could go on.
The irony behind that alternative option on Enterprise would've been, he was offered the chance to have his cake and eat it. He's the NX-01's mysterious Chef, a guy mentioned a lot (but never seen)... Somebody as far from Kirk as it's possible to get (the Shat playing himself), who is taken out of the past to be James T Kirk, at a critical moment.
He would've been Ace Rimmer, if anyone know's what the deal was with that on Red Dwarf.
Or more seriously, he's Churchill's double. A decoy and the twist is, he ends up becoming the real deal.
I think with some care, that would've been the funniest thing ever, with some drama about a legend being more important than just one man. Maybe more than writers (who are also his fans) just blowing smoke up his ass too.