I never liked them almost using "Gul" as his first name.
At the start of the dominion war he was #1 in charge of Cardassia but still a Gul? huh? How would that have worked if a legate tried to give him orders?
Of course when Damar became leader he was instantly promoted to Legate.
Would it have made sense to have kept Sisko as a commander just because they liked how that rank sounded better? Actually given all the responsibilities sisko had toward the end (single-handedly planning the cardassian invasion, etc) he probably should have been made admiral.