Tbh, I think the idea itself is not as important as the world that you create within your story, both internal and external. The easiest way to make your story stand out is to have a different setting, I did this pretty much for all my creatives since year 9 and its never failed me. Try setting it in a different place, time, or even both. If you make it work (ie you make the setting and the characters within it seem authentic) its very effective. Regarding the 'plot' my best advice is to focus on a moment in time, on a small event, a person's experience or even an emotion. Never do a short story that spans years (except for flashbacks), or worse, a character's lifetime. Also, make sure you know before you start what your story is saying about the notion of identity. Good Luck