I guess it's possible that peace reigns - most games I've seen people post here or talk about had devolved into nuclear armageddon pretty quickly since the number of active sensors causes relations to plummet pretty fast.
There are easy tricks for setting up the multi-faction start right. If done correctly you can even guide which one of them becomes evil genocidal and which don't no problem.(in my game I wanted China to flip out, Britain to be ambiguous-"can go either way", and Asean and South America to be peaceful, and that is exactly what happened. China attacked, Asean and South helped with PD + anti-orbital, Britain was neutral throughout everything)
Maybe I should create some tutorial post somewhere, since it appears this is not widely known. Not sure what I would talk about other than maybe documenting the exact stats of successful multi-faction games though, since it otherwise basically boils down to {Good guys: more diplomacy, little xenophobia}, {Bad guys: opposite}, and keeping active sensors off until actually departing.
I think you can even ignore the active sensor rule upon reaching ally status, but I generally do this in all games since DST stations far outrange any radar after the new C# formula once you reach 10-20 installations anyway.