I always thought the most interesting story that could feature Shatner as Kirk, would've been to place Storm Front
forty years later and in that reality Kirk, Spock and McCoy never escaped the 1930's from City...
. Archer would've teamed up with an elder Kirk who was now running the mission in Nazi occupied New York.
Before the timeline gets set right, an elderly Kirk gets a chance to step foot onto the NX-01 bridge and sit in the captains chair one last time.
I love this idea. In the hands of a talented writer this could have been a truly great episode. The best part of course is that Shatner would be actually be playing Kirk rather than a mirror universe counterpart or some lame look-a-like.
At the very least, they could turn that into a Phase II episode.