Replacing stock shots with new ones could do wonders.
Especially in the early seasons we got a lot of those, and a lack of starships made the station often look a bit isolated.
I could see them doing great stuff with really basic things like runabout take-offs, the wormhole or docking animations.
In some cases, they could really do cool new stuff. Like showing a "naboo" shot of a bajoran street instead of the standard Bajor matte shot.
DS9 remastered would have HUGE potential. An approach like TOSR would not do it justice.
Imagine the Earth shots with the tram train in "Homefront" replaced by a future Paris flyover!
Daaaang! That would be SO cool!
But you know what I'd almost kill for? Some really, really good Cardassia shots, instead of just that matte painting.
I think that also, in "What You Left Behind," we need an overflight of Cardassia Prime, post-bombardment. That would make Martok's actions look all the more grotesque, when he starts gloating and drinking amidst the carnage.