So if you think Worf could/should be captain . . .
1) Prove he has the diplomacy credentials and abilities for the post; not to mention the ability to keep a cool head. He killed the former Klingon Chancellor! (while in starfleet uniform, I think)
2) How can being in the house of the Klingon chancellor NOT be a liability when you foresee issues where starfleet and the Klingons will be at odds.
He was the Ambassador to the Klingon Empire for four years. That's plenty of diplomatic cred. Likewise, Starfleet has show that it will order a Captain away from a situation where they think that they're compromised in some fashion - First Contact, for example.
As for Data/B4, Nemesis itself set up for his return, far more so than TWOK did for Spock. I left that movie expecting a future return of him.
The way I see it, Data coming back through B4 shouldn't be an option in the first place. B4's systems just aren't that sophisticated. If I were to transfer files from my current computer, which runs Windows 7, to a computer that runs Windows 95, the best I could hope for when accessing my files would likely just be fragments. The same should hold true for Data's 'files' being transferred to B4.