So Caesar decided to go One-Winged Angel, just as Enel and Moria did. Not that I didn't see it coming, and it seems right that he would absorb Shinokuni to make himself "stronger". In One Piece though, transformations like these seem to be pointless, and only serve to make the enemy a bigger target to take out with an awesome finishing blow.
I mean Enel's was really pointless, as his electricity was null to Luffy regardless, though the extra trident allowed him to get some sort of damage in. Moria's was somewhat less pointless, and was basically an act of desperation, but at least he got some major damage in (although Luffy's determination and DF allowed him to shrug most of it off, not to mention Zolo ended up taking his suffering in the end.)
Caesar's….eh, I guess it has a point, but then it doesn't? I mean, yeah, since he's basically made out of Shinokuni now, Luffy wouldn't be able to touch him under Pre-Timeskip circumstances without getting poisoned and hardened (sorta like how he got poisoned from hitting Magellan.) But this is Post-Timeskip Luffy, and since he has Haki, can't he just envelop his attacks in it to shield himself from the effects of the gas, essentially making the transformation useless? Or am I misunderstanding how Haki works?
Basically the transformation is just for show, although it seems out of place in the New World, where Haki is supposed to be more common. Of course, it's probably just a desperate last minute attempt on Caesar's part, but that's dumb seeing as how it makes him even more vulnerable. Guess people just can't think straight when in desperation.