If you want a complete list, give it a few days. Otherwise you can find a few tidbits of realism ideas from me and other players on the other more popular ideas list.
I remember one of them brought up Lagrange points.
List your ideas for future updates below. Mine is suspension for rovers and drogue chutes for landers (parachutes for higher altitudes but do less slowing down than regular parachutes).
-Jet engines
-Small , extremely high thrust engine that has a built-in fuel tank ( used for escapes such as launch escape , stationary escape..etc....)
-White capsules, the black one is ugly as my old rocket i built when im new to the game
-Day-night cycles
-Smoke
-Realistic engine audios
-Better engine textures
omg im bright