I've had a lot I've wanted to talk about in the past few weeks as OP has been so brilliant, but this is the first point I've decided to make a blog about and it'll be short.
Franky told Luffy to remain incognito, and while it is totally possible that Luffy will forget this right away, reveal himself and get bogged down fighting DD's entire crew, I think he may heed that advice, at lest for a little while, mostly so Oda can explore this train of thinking.
Luffy, unable to use the Gomu Gomu no mi's powers. They would give him away imediately, so he'll have to rely on his strength speed and Haki. Picture this, the incredibly powerful Lucy defeats Diamante after a titanic struggle and claims the Mera Mera no mi for himself! Lucy, it seems has no Devil Fruit powers. As he raises the fruit high, he shouts "ACE! I'M GONNA BE THE PIRATE KING!!!!" And suddenly, Luffy's alter ego gets a higher bounty than him!