A first-person survival horror game where the enemies are all robots in a futuristic setting like a giant factory. The robots would come in a HUGE variety of shapes and sizes and would definitely not just be constrained to humanoid enemies. Some of the robots (Namely the security models) will attack you on sight, but other robots won't actually attack you unless you attack them first and will instead just endlessly toil on with their given tasks. Sometimes robots will go haywire and will begin attacking everything in sight. You can develop hacking skills to make robots calm and non-aggressive, but hacking is risky because a wrong move will cause them to go haywire. Stealth would be an important element; you can either use it to approach robots to attack them or hack them, or you can use it to hide from dangerous robots.
The story of the game would not be the protagonist's; instead, the protagonist would witness the fall of human civilization as they try to improve themselves with machine parts, until eventually many of them went haywire and the conflicting biological and mechanical parts began to rip each other apart. You also have the option of using machine parts to increase your combat, sneaking, or hacking skills, but each upgrade will bring you closer to that same fate. You just don't know how much closer; different upgrades will affect you more, with the best upgrades tending to be very risky. There are different endings based on how you handled the robots and how much you hacked yourself apart to improve yourself, but there is no indication of a sort of morality system. All of the endings do not turn out rosy for the protagonist, but that's just life.
Why will this game never happen? Look up the genre Survival Horror. :-/