On the other hand, Vulcan secession is a common theme in Trek novels. It's hinted at in Strangers From the Sky
as being the background of the infamous Vulcanian Expedition; it's the main theme of Spock's World
; it's one possible logical outcome in The Final Reflection
; and many of the post-ST6:TUC novels dabble on the fact that Vulcan has more in common with Romulus than with the Federation.
if Sisko wasn't supposed to be in charge of organizing the effort to bring Bajor into the UFP
That's an interesting if... That "mission", after all, is what Picard mentions in the passing in a private meeting between the two COs, while also emphasizing that Sisko isn't cleared to violate the PD in the process. The exchange in "Emissary" really sounds like Picard confidentially, almost conspiratorially, divulges the "real" mission to Sisko in stark contrast with his official Starfleet orders, which only involve managing the space station.