Since the role was originally created with Forbes in mind, I can imagine they would've adjusted accordingly.
Well, Forbes was going to play Ro (it would have worked liked Chief O'Brien).
It's hard to say how that would have played out, really. The entire show would have been different because Kira's involvement in the occupation and the resistance defines so many of the show's main storylines: Duet-Circle Trilogy, Terok Nor (starting in Necessary Evil
), the Occupation Arc, Kira goes to Cardassia, just to name a few.