@uniaka:
I imagine he/one of his crew has some crazy DF. Like he can control mind of others and use it to control marines so they bring DD to him.
Or maybe he can has a sneak sneak DF that can sneak in the marines's ship and take DD without notice. Maybe he would just have to beat Tsuru alone.
Aldo it would increase his chances a lot if Kaidou shows up.
Already answered here. Besides, Doffy is bound with sea stone and Kenbunshoku Haki would easily detect him. If he can swim they might confuse him with a sea monster, otherwise they'll notice him already from afar. Unless Jack can immediately move the whole room, a fight will occur.
@Daz:
I'm probably one of the rare exceptions here, but I personally found the first few pages of the chapter much more affecting and memorable than the rest. And not because of the Lucci cameo, even though him staying with the Cipher Pols makes a ton more sense than the CP9 cover story.
What makes you think he's with Cipher Pol? As I see it he intended to do the same as the Revolutionaries, so he still might be acting independently with his team.