This is a story idea I've had in my head for a few years and I thought the foundry was the perfect way to finally use it. Problem is it's just a basic idea, not a fully developed story. Basically you detect a new warp signature and go to meet the species that created it. As you explore their culture you begin to suspect that they're hiding something. You eventually find evidence that long ago the species became aware of the Borg and after further investigation discover that they have been working toward a way to capture and harness Borg technology. You confront the world leaders and try to make them stop, but soon a Borg invasion starts and Starfleet sends a task force to assist your overwhelmed ship in stopping the invasion. After a narrow victory you inform Starfleet Command about the new species and what they are doing and face a tough decision regarding what to do with the species.
So that's my idea. I think it has a lot of potential as a TNG-style story but obviously I need to flesh it out. I read an old TNG novel called "The Last Stand" which deals with an emerging culture hiding a big secret but I'm still stuck on specifics such as: what is the new species culture like? What are the clues and evidence suggesting ancient Borg contact? How are they planning to trap the Borg and how are they luring the Borg to them? What would the Federation do with such a dangerous culture? Send diplomats? Violate the Prime Directive by trying to redirect the new species culture toward non-Borg ways of advancement? Quarantine the world like they did to Talos IV in the original series, thereby isolating the new species from the rest of the galaxy forever?