Here is my small contribution as an appreciation to C.J.Cherryh.
Oxigen Factions
Methane Factions
- currently methane-breathers do use synthetic setup as placeholder
- I'd really recommand to have those 3 methane factions in 1 team for better experience
- as tribute to author's original creation you may avoid any interactions with chaotic Knnn or crazy Chi 
- as soon as something like gas planets are playable, those factions get reworked
Download:
(manually dl no longer upgraded, pls use Workshop Collection)
(as a hint: manual files should be placed C:\Users\[YOUR NAME]\Documents\my games\GalCiv3\Factions )
Graphics Complete
Factions Complete
As for Opt-In Version 1.1 the factions are availible in a Workshop Collection.
Cheers!
Some of my other factions you may find at [Mod] custom factions basket