The beauty of fan fiction is you can do whatever you like. If that's the design that moves you, go with it. As a fan fiction writer myself, I don't like using other fan fiction writers ideas without permission or at least acknowledging where the idea came from. And definitely I would not use another writers characters unless I had permission. It's fortunate that I'm part of writers group, United Trek, where we pretty fairly use each others characters, etc., but even then, we sometimes will ask permission or have other discussions about things that could affect our shared universe.
Long story short, if I were you I wouldn't get hung up on your work being similar to someone else's. We are already playing in someone else's sandbox anyway. And where you can really make your mark is in your characters and eventually how your stories will progress to set your series apart from anything that inspired it, or you are concerned, might be too similar to it. One thing to do is, if you have a series in mind you think is very similar to what you want to do, is to look at their characters and stories and then try your best to do something different or opposite.