I think it would be awesome to have airlocks that can be opened and “suck” players out into space where they slowly suffocate. This would add realism to combat in space.
It would also be awesome to have maps that have realistic blackholes in them, obviously of artificial nature and of a small mass. Falling into one or being pushed by another player’s lucy shot should make an interesting view as one is spheghettified and redshifts. The player’s point of view would have some fun and interesting light distortion as they fell inward. Death by blackhole would be an interesting way to kill an enemy player in Trem.
Also realistic asteroid impacts in trem could be a fun element of tremulus maps.
Space radiation could play a part on some maps also.
Just some fun and interesting ideas I thought I would spam out there.