@brennen.exe:
Yeah, see, Stephen's translation just says, "Ace, the man who had chased me down for my crimes on Whitebeard's crew, happened to be your brother!!" So no implication at all.
Ok you are right, then we don't know at all if he knew, in fact he probably didn't..
You tell me. He mentions it twice, which is why I emphasized the "mid battle regret":
[440] Blackbeard: Let me just say one thing, then.Ace!! Will you join my crew?!! Come and seize the world with me!!!
[441] Blackbeard: Everything is powerless before the dark!! Even someone as strong as you! Tell you what, I'd hate to lose ya…!! C'mon, Ace...!! Join me!!!
It's a pretty brilliant patronizing line. Shanks says something similar on Whitebeard's ship (ofcourse it is less mean-spirited because the situation is different). Blackbeard is basically telling Ace "I am superior to you, but hey kid, you are good enough to serve under me."
My point was that capturing Ace was a change in fate for them. A notable one. That could mean anything, but I am suggesting that maybe it meant fate was guiding them down a much quicker path to their goals. It's kind of a stab in the dark, but were it true, it would make sense and would have been "hinted" at.
Maybe so, but the same was said about Enies Lobby, and look what Luffy did. Regardless, I still don't think his title helped at all in getting to Impel Down, and even if we pretend that getting a battleship is otherwise impossible, the biggest problem I see is that in any non-war time Blackbeard would be facing a fully staffed prison and a completely aware and responsive Marine force. He was lucky in this case only because both parties were completely distracted. Any other time would have been the understandably impossible situation Nyon was referring to.
He would have had to wait for a similar distraction sure (we know he's a patient man) so 'fate' could have sped up his plans. But it is really hard to say since we don't know what his real plan is.