In some biomes (f.e. - Snowy Tundra) engine can freeze, and you can't start it until it be heated up. For pre-launch heating you can install individual (for each engine) electrical or fuel preheater, it can be activated from control panel like engine (switch). It will add some realism, you can't easily start engine in very cold place.

While this sounds nice at first, I can't see most players enjoying it. I can only see it being the start of a long stream of "why can't I start engine" complaints. As such, I'm going to flag this as a wontdo.