Would these be cool things to have or is that just me?
Like have night time maps and the vehicles can have little headlights and stuff.
Rainy maps.
Snowing on snow maps?
Weather effects/night time?
Try out https://github.com/chrisforbes/OpenRA/tree/weather-test for a rain map with thunderstorm.
See https://github.com/OpenRA/OpenRA/wiki/Compiling to get started with coding.