I have an idea for a hard sci-fi DayZ (I know, I know) space game.
MP, set in an asteroid belt, you start in a small pod with limited resources you have to make you way around the belt to various abandoned space stations, derelict ships, asteroid belts etc collecting O2, propellent, gear, food and water and upgrading parts in your craft adding sensors, thrusters, weapons systems.
The combat and movement should be very cat and mouse stealth based, you have ECM, IR, UV, Active/Passive radar systems for sensing and different gear on your ship should generate signatures when used, for instance a weapons system might increase your heat signature when fired or when you use thrusters to adjust velocity.
I'd like to get a feeling similar to the space combat in the book Redemption Ark by Alastair Reynolds. Where you're holding back that 1 salvaged IR missile or those last few rounds of gatling cannon for the exact right moment when the other ship comes out from the asteroid's shadow and the light makes it targetable.
I'd imagine there would be rogue AI in the place of zombies, active minefields, sentries, turrets etc to complicate things.