For me, I'd have loved to have seen the station under it's original premise, a much older facility used by several races over the years, added to and altered, giving it a more mish-mash feel for the Starfleeters to have to deal with. It'd also allow for some interesting stories about the base itself and the long, mysterious past (as well as what might have been left undiscovered/forgotten within).
Character-wise, as much as I like Ro, I think Kira was a better addition, giving a totally different perspective and objective to the typical Starfleet mentality. Sisko wouldn't change (except maybe give him the goatee from the beginning), though I think it'd have been interesting to switch Jake's gender, to give Sisko a little something more to worry about--especially the friendship with Nog and how that would develop with a hew-mon female. I'd have added a little more with the O'Brien family, looking at the strains of the new assignment on their family, he of course would still have to deal with all the crap the universe can throw at him. Quark would forever be Quark. Odo I'd like to have seen as more of a private investigator, further isolating himself from the rest of the population, though still a close friend of Kira's (who is always willing to fight his corner). This would see a new Security Chief, though I'm not sure if I'd go Starfleet or Militia as both have their own benefits and drawbacks. Bashir wouldn't change much, still the cocky and somewhat-arrogant rookie who becomes more seasoned and level-headed over time. Dax would start off as her more adventurous self, embracing all that life has to offer and cracking off one-liners. I'd also like to see Pazlar added, though now as Counsellor (I'm tempted to switch their gender as well), seeing as how Sisko would have problems to overcome, as well as being a cultural expert who can help study the station.
