We actually banned kidnapping in our overarching plots because so many people wanted to be kidnapped and it was getting exhausting XD. We don't get a say when people do their own personal stories or one-offs so it still happens quite a bit.
On "Stories shouldn't revolve around one person". If you CAN, you should make a story that doesn't really have a main character at all. Nothing from anyone's backstory (Unless it's a shared backstory with more people involved). You can have people who can be integral at the START to get it off the ground (Then let the story be free to go toward whoever grabs for it) but none of them should be the single focus of the plotline. I know this can't be avoided all the time (Hell, we're guilty of this right now) but it's good to START with a more neutral plot line that anyone can jump into without having to know <insert character here>. Once trust is established, you can absolutely branch off into more personal storylines.
On "One-offs are better". I think that really depends on the RPer. There are a lot of people in my guild who really like long, overarching plots and there are some who don't really have time for that and can't participate, and some even still who don't like keeping track of the madness and just wanna punch some baddies sometimes. If you're looking to do the first thing, I suggest actually doing BOTH. It's actually really easy to put one-off plots within your overarcing storyline. Lets say your bad guy uh... We'll call him Bob, is threatening to do SOMETHING with some ancient artifact that may hurt Eorzea! But you don't know much on what that artifact is! What do you do? A one-off dungeon run into the great Library to look for info may be the best bet OR if you have more time - a one-off roll20 into some ancient ruins to find more information. Then you find more info on how to stop Bob, but alas you don't have the right pieces to make thing you need! And the pieces are illegal and hard to find in Eorzea! You can then do a one-off about smuggling the pieces in.
These are all things that would work separately ("Finding info on artifacts" "Smuggle in goods") without a plot, so people without a lot of time or inclination CAN participate, but they also circle back to your overarcing plotline for those more deeply involved. These aren't events you have to run either, if you have some active members they may just volunteer to run it and ask you what they would find when they do. A lot of one-offs my guild does are run by other people who want to help find answers... though you may not get to many people volunteering at the start.
On "Stories shouldn't revolve around one person". If you CAN, you should make a story that doesn't really have a main character at all. Nothing from anyone's backstory (Unless it's a shared backstory with more people involved). You can have people who can be integral at the START to get it off the ground (Then let the story be free to go toward whoever grabs for it) but none of them should be the single focus of the plotline. I know this can't be avoided all the time (Hell, we're guilty of this right now) but it's good to START with a more neutral plot line that anyone can jump into without having to know <insert character here>. Once trust is established, you can absolutely branch off into more personal storylines.
On "One-offs are better". I think that really depends on the RPer. There are a lot of people in my guild who really like long, overarching plots and there are some who don't really have time for that and can't participate, and some even still who don't like keeping track of the madness and just wanna punch some baddies sometimes. If you're looking to do the first thing, I suggest actually doing BOTH. It's actually really easy to put one-off plots within your overarcing storyline. Lets say your bad guy uh... We'll call him Bob, is threatening to do SOMETHING with some ancient artifact that may hurt Eorzea! But you don't know much on what that artifact is! What do you do? A one-off dungeon run into the great Library to look for info may be the best bet OR if you have more time - a one-off roll20 into some ancient ruins to find more information. Then you find more info on how to stop Bob, but alas you don't have the right pieces to make thing you need! And the pieces are illegal and hard to find in Eorzea! You can then do a one-off about smuggling the pieces in.
These are all things that would work separately ("Finding info on artifacts" "Smuggle in goods") without a plot, so people without a lot of time or inclination CAN participate, but they also circle back to your overarcing plotline for those more deeply involved. These aren't events you have to run either, if you have some active members they may just volunteer to run it and ask you what they would find when they do. A lot of one-offs my guild does are run by other people who want to help find answers... though you may not get to many people volunteering at the start.