The one thing that bothers me is how Luffy will beat Ace.
Rubber burns quite easily. And when it does, it has the most godawful odor you can imagine.
Didn't Luffy threaten to kill the Kuroneko Kaizoku several times? I believe he said, "Laugh at Usopp again and I'll kill you." And Zoro killed Siam and Butchie and Luffy didn't even care.
Luffy doesn't murder senselessly. Neither does most of the strawhats. Only Zoro and Robin really kill anyone. Robin because she didn't trust anyone till the Strawhats and Zoro because before he met Luffy, he was a bounty hunter, which is the same thing as a mercenary. You're paid to apprehend and/or kill deadly criminals.
Luffy doesn't really care who dies as long as it's not the person he's fighting. He's a bit of a sadist, actually. Luffy wants his victim to remain alive so that they suffer the pain of regret, the realization that their dreams have become corrupt and will not succeed if they continue down the path they are going. Even the nasty Arlong had a dream…
But like I said, Luffy witnessed several deaths and didn't give a rats ass about any of them. The only death he cared about was the Bounty Hunters at Whisky Peak. Luffy's gullible, so he didn't think to realize that people that had been so nice to him were actually tricking him. Plus, he knew Zoro was a killer.
When Mr. 5 blew up Ms. Monday and Mr. 9, Luffy didn't care. When Igaram got killed (supposedly) by Robin, he didn't care. Luffy didn't care when Pell (supposedly) or Chakra died, either. And so on and so forth. Luffy acts dumb, but he's not. He knows that death is inevitable.
One thing that puzzles me, though. Back in the Krieg Arc, Luffy told Krieg he wasn't going to die, and to Sanji, told him that getting killed was no way to repay a debt. However, when Lucci mentions that the "Gear" moves put great stress on his body and will drastically shorten his life, Luffy seems a bit different. He says that it's inevitable and he'll do what he can to protect his nakama. For Vivi, too, he was "killed" twice by Crocodile, but came back and still fought.
Has it ever occurred to anyone that the D may mean that they have control over life/death? That the D's can CHOOSE when they die? D. Ragon saved Luffy in Loguetown, but nothing saved him from being impaled in the desert except his own will, and being dehydrated by sheer luck.