Star Trek: Deep Space Nine was never going to replace Kira Nerys with Ro Laren

Star Trek: Deep Space Nine was long seen as a series that would spin off from The Next Generation. Like its predecessor, it would air in syndication and would feature a few characters from The Next Generation to help fans get acclimated. The series was going to be built around Benjamin Sisko, a commander on the station, who was dealing with the fallout of his wife's death while raising his son Jake.

The other core character was going to be Ro Laren, a character that debuted in the later seasons of The Next Generation. The character was Bajorian and left Starfleet to help the terrorist outfit, the Maquis, fight the Cardassians for control of Bajor and its subsequent territories. The show would see Ro return to the Federation after the Cardassian occupation of Bajor ended, and come to terms with the events of the war, and what it meant for her people.

Sadly for those who were interested in that story, the actress who played Ro Laren, Michelle Forbes, wasn't interested in being locked into a long-term contract and turned down the role. So instead the creators of Deep Space Nine created a stand-in character, Kira Nerys. Kira never served Starfleet, but besides that, her backstory was identical to Ro's. She was a freedom fighter on Bajor who fought the Cardassian for years and accepted a position with Starfleet as a sort of ambassador to the Bajorian military and an ally to Sisko.

She was the solution to the problem of "How do you replace Ro Laren". At no point, contrary to misleading headlines, was Ro ever considered to replace Kira. It's important to state that, so people know the order of events. Kira was not the original idea for the character but after Forbes turned down the role, the crew tapped Nana Visitor in, and she absolutely nailed the role. Is she the "best" hero in the series? Who's to say, each main character has their own right to take claim, but we're certainly glad that things happened the way they did.