Re: Ro Laren
As much as I love Ro, DS9 would not have worked with her in Major Kira's role, and I don't think it would've taken the producers long to realize that regardless of their original intentions. Sisko's role as the Emissary is the 'narrative foundation' for the entire series and you therefore need a deeply religious character to play off of him, and Ro could not have been that character. You also need a 'native' character (someone whose only emotional ties are to Bajor) for the show's premise as 'a Wild West frontier town in space' to work and Ro doesn't fit the bill there either.
Starbuck: We're all friendlies. So, let's just... be friendly.
"There is no 'supposed to be.' It's an adaptation, a word that literally means change. Why bother making a new version if it doesn't offer a fresh approach?" - Christopher L. Bennett