DS9 will always be the toughest sell to networks. Heavy serialized shows have a very hard time getting decent ratings in rerun syndication. While DS9 might be a more richer experience for viewers it requires the most commitment to follow. But viewers tend to get fed up waiting every week for the next episode, while episodes of TOS or TNG can be seen entirely out of order with no problems. Trek was born to be episodic, the reruns of TOS was what kept the franchise alive for decades until we got new material.
I can see CBS doing VOY before DS9.