Just throw it all out...
This is something I'm throwing out here out of bordom and curiosity. My own plug development teams has decended into vaporware, and currently I am a graphics artist with nothing to do. The idea behind this topic is that everyone throws a plug idea out, then we chose the best one's and refine the ideas. Once we're done, we should have a plug that everybody would like to see, and from there, we could form a team and attempt to create said plug. So, fire away!
Starting simple here, a plug called 'The Arbiters', in which those in the Nova universe encounter alien beings that have been watching their progress for some time. As they initiate contact, they infiltrate even the smallest parts of the human colonys, and everything quickly decends into bedlam. It would be up to the player to form a rebellion with whomever he/she can find, and drive the vastly superior alien forces out of the Nova sector.