I am uising RSO 1.5.6 and latest download from Dytech and when i am creating a new game, it says that a lot of resources are not available. I suppose it is link to RSO no ?

Ok thanks for the information.

Mod seems very interesting ! In the original post, it is said that it could corrupt our actual save. Is it still the case or is it secure to use it ?

Will it not be possible they evolve more with time ? (especially for MP end game)
Meaning they could become "intelligent" beings in their own way with the time and tried to start some kind of technology ?

Definitely different wagons types and underground belts.