Be warned that the relevant story is only a couple of pages long as part of an "anthology" issue.Definitely going to have to check out the Mitchell comic, then - there has always been speculation that he could/should have survived his fight with Kirk, so imagining him as a cosmic entity decades later is about the easiest leap for me to ever make with Star Trek.
Though if you get it, definitely check out the story Wil Wheaton wrote! It actually hinted at some of the canon stuff that was coming out about two years before the relevant episodes were released.