Recasting made no sense. There was no reason for Ro Laren to be the only Bajoran in the Trek 'verse, and she was already written out of TNG. Though, yes, there was an obvious setup for her to show up somewhere on DS9. I think a recurring role as Maquis Superwoman would've worked well on DS9. She could've very easily been a regular given the premise of Starfleet and Maquis forced to work together. Didn't Chakotay basically ape her backstory about Starfleet officer gone Maquis? Anyway, given that the Starfleet/Maquis tension didn't really last much beyond the pilot, Ro on Voyager probably would've been just as disappointing as the rest of the show.
Actually, she was only written out (and defected to the Maquis) near the end of season 7 of TNG, when DS9 had been going on for almost two seasons already.
Chakotay didn't have the same backstory, since he resigned from Starfleet before joining the Maquis. Ro's situation is more similar to Eddington, Cal Hudson or Tom Riker, who defected while they were still Starfleet officers.