Yeah, with Ro and Kira being so similar, it does feel a little redundant to have Kira leave, and then just put Ro in charge.
I see it more like Ro is replacing Sisko, and Cenn is replacing Kira, in spirit if not in function. With the Ro/Cenn command team, we now have the same model we had when the TV series started - a Starfleet commander who has a connection to Bajor that they do not entirely embrace, and a Bajoran Militia XO who does not believe Starfleet has any business being there at all.
With Bajor being the in Federation now, there are still plenty of other things she could do in the system if she wanted to leave DS9. She wouldn't even need to move up, she could just move to a similar position somewhere else. But there's really no reason she would have to leave the station in the first place, we've seen plenty of people commanding the same ship/crew for decades.
To me, it was never Kira's dream to be in Starfleet. She had any number of chances to convert, Sisko would have sponsored her in a second if she asked. But even after her objections to Starfleet's very presence died down, she had no particular desire to be one of them. She converted when Bajor finally joined the Federation at the end of 'season 8' mostly just because it was what was expected, not because she was thinking, "Finally!"
Then her character arc in 'season 9' is about trying to figure out if she is good enough to be a Starfleet captain. The conclusion is obviously that she is. But then her character arc in my 'season 10' was the next question in line - yes she can be a Starfleet captain, but does she want to be? And the answer to that one is no. When there comes conflict between the way Starfleet does things and the way Bajor does things, she would choose Bajor every time.
Ro, on the other hand, doesn't have as close or instinctive a connection to Bajor, which is why she doesn't have the same conflicts with Starfleet. She has whole different conflicts.

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