There is no replacing William Shatner's Captain Kirk. Shatner created a character that, to this day, is the embodiment of the quintessential captain. It's a hard role to fill, and that's why, to date, no one has really tried to play Captain Kirk Shatner's way. One Star Trek: The Next Generation writer, Melissa M. Snodgrass, wanted to make Data [Brent Spiner] a little more like Kirk, specifically in the episode "Ensigns of Command." [via GiantFreakinRobot]
In the episode, Data is in charge of moving colonists from a planet. Snodgrass had it in mind to "stress him and have him face a situation where logic isn’t enough, to show that in order to command you have to have charisma.” The type of charisma that Kirk had, of course. But that didn't happen because the script went through rewrites, and Snodgrass wasn't happy about it. She even used the pseudonym "H. B. Savage" for the writer credits.
Snodgrass wanted Data to be more in charge and "have to learn how to wave your d*ck and hope your d*ck is bigger than the other guy’s.” But that takes away from Kirk as his successes came partly from charisma, but he was also a great leader. He cared about this crew, had diplomacy down to an art, and could make decisions quickly and efficiently. One great example was at the end of season two's "The Deadly Years." Kirk comes onto the Enterprise's bridge and only has a split second to learn what's going on. Seconds later, he gives a command to Lt. Uhura that has the Romulans retreating.
Had Snodgrass really wanted Data to be more like Captain Kirk, she could have focused on that side of Kirk, and perhaps the powers that be would have left the script as it was. Snodgrass, who also penned the successful "The Measure of a Man," ended up leaving The Next Generation after season three because she butted heads with the showrunner, Michael Piller. And Data stayed just the way he was meant to be, learning and growing as the years went by.