Lets suppose Captain Kirk goes to bed and wakes up on board the Millennium Falcon in Mos Eisley, Tatooine at the beginning of Episode IV. Han Solo goes to bed on board the Millennium Falcon and wakes up in the Captain's quarters on the Enterprise. What do you think would happen to these two characters?
With Kirk leading the rebels, the Empire is crushed during A New Hope. With Han Solo now in command of the Enterprise, the Federation falls into disarray by the end of the TOS's third season. Also, Spock's brain is never recovered, with Solo siting Spock's new brainless personality as a vast improvement.
Probably what would happen is Han Solo ends up in the Brig of the Enterprise as soon as he is discovered. Kirk would have trouble understanding Chewbacca, Chewbacca would want to know what happened to Solo, of course all he could do is go "Arrrrgh". Chewbacca and Kirk would in the meantime need to earn a living, C3P0 would be most invaluable to him as he could speak Wookie and act as a translator. It would be easier for Kirk to command the Millenium Falcon than for Han Solo to command the Enterprise, as he would be deemed an intruder and a suspect in the disappearance of Captain Kirk.
Kirk would have charmed Leia into his bunk before they even reached Yavin IV. And Darth Vader would have been soundly defeated by a Kirk-fu chop.
Kirk really is more efficient than Solo, isn't he? I'm pretty sure that Han Solo would be able to be accepted on the Enterprise, because he oozes roguish charm, and that works wonders in the Star Trek universe, but he'd sell the Enteprise pretty soon, wouldn't he? Or he'd lose it in a bet? Kirk, on the other hand, would be a fantastic asset to the Rebellion, and with his help, the Alliance would have been able to win the battle of Yavin with or without Jedi tricks. And I really don't think that the Empire would have been able to find the Rebels on Hoth if Kirk were calling the shots.
Kirk also has an engineering background and might be able to coax something interesting out of the Falcon's engines. But if he ever got himself in a tight spot and expected a rescue using the Falcon's transporters, he'd be out of luck. "Chewie, beam me up." "Raaawwwr?" "No, really, beam me up now!" "Raaaawwwwr!" "What exactly does that mean, anyway? You keep saying that." "Raaaawwwr."
Kirk doesn't need to shoot first. He takes out Greedo with a flying karate kick. Han will get dumped off at the nearest starbase, where his best move is to partner with Cyrano Jones in the lucrative tribble smuggling trade.
Han Solo wakes up in the brig. Kirk defeats Vader, gets Leia, destroys the Deathstar, kills the Emperor, and breaks up with Leia before the end of the episode.
Just like in Star Trek "James T Kirk" the ultimate deadbeat dad,fathered hundreds if not thousands of kids in every corner of the quadrant.
Spock: "It was easier for you, a highly trained professional Starfleet officer, to pretend to be a ridiculous moronic gunslinger. Than it was for Han Solo, a ridiculous moronic gunslinger. to pretend to be a highly trained professional Starfleet officer. Kirk: "And so you threw Han Solo into the septic fluid recycling tank?" Spock: "It was the logical thing to do." Bridge crew breaks out in laughter.