Well this is just an update. I wasn't planning to start this story for a while but a particular review from Jack Tennant was so enthusiastic that I at least wanted to address some questions he had.
Does Luffy have his straw hat with him? The answer is no. Just like how Naruto always has Sasuke's headband, Nami would have Luffy's hat. It would become her most treasured possessions. However at some point, Luffy would meet his ex nakama and several other close allies like Vivi, Shirahoshi etc. And right in front of them Luffy would rip the hat in two. This shows Luffy has completely given up on the pirate king.
Will Luffy meet Shanks, Rayleigh etc: Yes. Shanks is a yonkou so he has one of they keys. Also a few keys are in Paradise as stated before so Luffy would have to go to Sabody Archipelago at some point. Rayleigh would be killed by Luffy. The reason why Luffy decides to spare allies like Vivi while killing those like Rayleigh is because people like Rayleigh are strong. Luffy can completely ignore Vivi since she can't do anything to him. Vivi is too weak to make Luffy listen. However guys like Shanks and Rayleigh are super strong and Luffy would have to kill or else he himself would die. The fact that he did kill his hero Shanks and teacher Rayleigh would show how far he has fallen. Garp would die too since Luffy would have to kill him to further go down the dark path. Also experienced guys like Garp, Shanks, Rayleigh even though they are close to Luffy are mature enough to try and kill him so Luffy would have to kill them first. The straw hats, Viv, Shirahoshi etc while may be strong cannot bring themselves to kill Luffy so he could ignore them.
The 9th key: I don't know where it is for now but at some point it would fall into the hands of the Straw Hats. I mean strong allies like Shanks, Rayleigh, Garp would be killed by Luffy. Obviously they cant go to other strong guys like BlackBeard, Akainu since they are enemies and would die by Luffy anyway. They are the last strong guys who could protect the final key.
Would Luffy have Ace's fire powers: Yes he would. Actually I intended that from the start. Sasuke too is brothers eyes, so Luffy should take his brothers fire powers as well. Also his techniques would better simulate Sasukes. Luffy's observation haki would simulate the Sharigan's prediction abilities but no illusions. Ace's fire powers would simulate Amaterasu but not as strong and Luffys arnament vulcanization would simulate Susanoo. However Luffy would not gain this ability for a while. And even if he does, he would not be overpowered. While the fire powers do a lot of damage, Luffy's rubber powers are significantly faster than fire. Also he cannot use haki in the fire attacks. Finally Luffy cannot let attacks pass through him.
Would Luffy get BlackBeards powers: No. The reason Luffy would get the fire powers is because Dragon helped do it for him. Luffy cannot do it himself. Just like how Madara had to do the operation on Sasuke, Dragon would help do it for Luffy. Dragon however I've decided to give him two devil fruits. A paramecia storm storm fruit and a logia water water fruit. The two make him the strongest in the world and final villain. Also even though he is so strong, he is no invincible which is why he hasn't destroyed the World Government already. He needs to plan and manipulate the be more like Tobi. Also his powers are much smaller than Uranus. Uranus would be several times larger than even several giant sea kings together so that's why he needs them.
So Jack I hope this clarifies some things. Hope to start soon.