I got into writing fan fictions quite a while back but lost interest in it after a few years. I had started and gotten quite far into one that followed more of a 'One Piece movie' format, with lots of one-on-one fights that sort of ended pretty quickly as is the way in limited-run movies, and a story designed to be self-contained. It was post-Franky but pre-Brook so it didn't have anything from during or after Thriller Bark but I thought it was pretty good. I doubt anyone here has heard of it (it was on Mediaminer.org, I think), called "Cursed Island of the Devil Fruit Gods" or something, been quite a while since I last looked back there. Basically I wanted something where each person on the crew, whether in teams or otherwise (including Smoker and Tashigi thrown in for laughs), takes on a Logia user and triumphs. Also wanted the main boss to be a lava/magma monster (imagine my disappointment when Akainu showed up in the manga). Anyway, I thought it had been pretty creative how I devised weaknesses for each of the Logia users before the advent of Haki.
I had an idea for another one that I never even started but I wanted to at least see what people thought of the concept. I know it's not a new idea, the premise for this one but I thought it was a good setup for a scary alternate future type of thing. Here's what I was thinking, and it's just a short-ish description compared to the actual narrative that it would otherwise be:
The crew is in a big firefight on the ship against some hardcore bounty hunter types and there's lots of DF powers being thrown around. One of them is some kind of time warping thing and in the fracas, Usopp is thrown overboard, falls through one of these wormholes, and awakens in a future a little over a decade beyond the events where he fell off the ship. The world is different, peaceful but in more of a 'you get out of line and you die' sort of way (think the Justice Lords episodes of Justice League). Usopp sets off to find what happened to his friends. He first meets Sanji, but only by accident. He runs into a ship in the middle of nowhere called "The Shitty Restaurant" run by a dumpy little bald man with a crutch and severe limp. He doesn't recognize him as Sanji, but Sanji never forgot Usopp. It turns out Sanji did find the All Blue, which is where the floating restaurant is right now. Only, all the fish are gone. Luffy liked them so much he had them fished to extinction to feed his endless appetite. Apparently Luffy changed more than anyone after they lost Usopp and all went their separate ways.
Usopp departs Sanji's place and gets caught in a storm, nearly drowning but he's rescued by a small, low-flying cloud island covered in orange trees. His rescuer, a one-eyed Nami with an eyepatch, greets him and tells him she's no longer obsessed with money because of how much things have changed, and she prefers to just be alone after what happened with Luffy. Usopp is now far more curious to find Luffy and try to help since he seems to have taken a turn for the worse, beyond anything any of them could have imagined.
He moves on and meets Franky and Chopper, who are in even worse states than Sanji and Nami. Chopper apparently had some kind of brain surgery to turn him back into his animal-brained self so he no longer had to live with the knowledge of everything that happened and is just a normal reindeer again, living on Franky's farm where no technology exists because Franky gave that up too, and is a frail old man without his cyborg implants, just using the bare minimum to keep living. Usopp moves on to a settlement with heavy Marine presence and is captured for not having any sort of identification on him which is illegal. This brings him to the attention of some old friends who are now working for the Marines.
Zoro and Robin are married, though it's more of a political marriage and they are both also Shichibukai. They identify Usopp and place him under their protection, and explain what is happening in greater detail. The Marines are under new management, namely working for the Pirate King, Luffy. They're even more ruthless than in the old days because Luffy blames what happened to Usopp on the reputation of other pirates who gave those like him a bad name. Luffy himself is a giant, having gotten used to stretching himself out to the point where he can stay enlarged at all times, and he's in the same condition as Whitebeard, hooked up to medical machinery and being attended by medical staff constantly. He demands great amounts of food and tribute and so the majority of the world is starving because of it.
So Usopp has to try to get through to Luffy and change things for the better if he can't get back to his own time. Fortunately Luffy has a collection of Devil Fruits from all the slain users and one of them is the one to create time warps so Usopp can return to before he traveled through time and stop any of it from happening.
I dunno, it sounded cool when I thought of it. Just watching everyone hit absolute rock-bottom in ways Oda probably hadn't even considered.