Feel free to share your ideas!
How about to have some types of civilizations? You can develop thanks to analogue of fuels(algae, if it is, or something other), thanks to oil, or thanks to microbes (or something similar). All ways have their pros and cons. When you use oil, you develop fast but with with disastrous consequences (up to environmental disasters, if you don’t take action). If you will use analogues of oil or fuel, you will develop slower than with oil, but after the threshold you will develop faster and faster. And that without disastrous consequences.
Yeah I think it would be really interesting to see how a civ would develop without oil. I’ve heard people argue that if civilisation collapses now then it will be super hard to rebuild because oil is so much more scarce now.
I heard in one TV program: that people will use algae, if will no oil. And another idea, civ in style steampunk. It will be with steam engines, airships and other things in steampunk style. I think, that it will be cool! 
Necroposting! Mwahahahahahahaha!
*double necropost
Fascism shouldn’t be in the game, atleast not name-wise, because the name comes from roman fasces. While yes, some stuff would deffinitly not be called the same, but fascism is something that has bame based from something from history and isn’t a new word or combination of words. I have few alternatives to it:
National rejuvilation
Ultranationalism
National totalitarianism
Right wing authotatlianism
And much more
Not calling it fascism is plainly ridiculous, considering it is the for most recognized term, a fasces isn’t exactly a common known symbol, and the logic of not using real word terms would mean we couldn’t call magnets that because it’s derived from Magnesia(A place in Greece).
Gameplay-wise, it should probably be included, atleast in minimal form for how important it is historically (and to sate the bloodlust of 4x players).
Fine then.
Conquest is unirronically fun
Maybe there could be nukes. If they are used to often they could cause a nuclear winter and civilization is set back to the beginning of industrial stage but with much worse enviromental conditions. Perhaps this nuclear winter could erase or change the already existing cultures and completely now ones could form.
If nations don’t want this to happen they could make agreements to not use nukes.
Cold war situations could happen if some nations gained acces to nukes.
Maybe some species will discover nuclear technology much later and cold war situations don’t happen because no one is afraid of a nuclear winter because there are no nukes.
i really wonder how nukes’ll be handled. i’d assume they wouldnt have to be society destroying, before the arms race between the USA and USSR no one had enough nukes to end a single civilization and had no need to. nuclear deterrence before MAD was just having enough that the enemy would have to loose a few cities or its army or something. MAD was never inevitable and could have stayed a far off theory, and tactical nuclear use was actually possible before MAD. I’d love to see how that would play out.
Terrain Modification: Players will be able to slowly shape terrain to create structures like canals or tunnels
Cold war in a alien planet could be a great idea. like the cold between USA And USSR