Re: What if Gary Mitchell didn't die?
He would have played the roles of Bailey in "The Corbomite Maneuver" and of Lt. Styles in "Balance of Terror". Possibly someone with an attitude like "hit them hard, while we still can" or "fire first and ask questions later".
Come to think of it it might have been pretty interesting.
"The first duty of every Starfleet officer is to the truth" Jean-Luc Picard
"We can't solve problems by using the same kind of thinking we used when we created them." Albert Einstein