The obvious answer for me was Bottlecap Galaxy.
Have I talked about Bottle cap galaxy? God damn we're working on so much.
BCG is basically: CosmoGnomic Gnomads are scavenging the Garbage Belt where humanity has been dumping their trash. They have been recycling human trash into spaceships and garbage deflectors (in the form of bottle cap launchers).
My initial thought was that you'd have a virtual Cosmognome living in your little keychain who spends his day collecting "debris" as you wander around, and using that debris to build stuff.
If you encounter other folks with cosmognomes, you both get to jump ahead a slot on your research tree.
Then the idea was to render various garbage deposits around the city, and have the gnomes turn those garbage deposits into functional pieces of gnomic society by interacting with them (but then I'd need a mechanism for continued play! What do you do when all the garbage has been converted into gnomehomes?)