You need to come up with a story, plot. And move in small steps in that direction. Players in the Game are not at home. And he is needed, the stations are not clear, but the house is needed. Develop infrastructure on the planets. And for this, engineers, resources and their extraction are needed. There is already a reason to attack and defend the planets, humanity has always been belligerent, but the invasion of alien species will force all of humanity to unite to defend their territories.
Possibly one star system is not enough, for such a scale, you are already developing other systems. The game must have a cyber sports mode, quick matches, for example, one team delivers artifacts home, the other must not allow this. I would not recommend introducing new modules and tools so as not to upset the balance. You need to develop a game system for different Players, someone likes to fight, and someone builds it, but for a getter, you need ships and modules for crafting minerals. Redefine earning loans. An alien species must have an advantage in development, and carry a very serious threat. I think the Alien species is Artificial Intelligence. Out of the understanding of the humanoid species. And for this conflicting faction will have to unite to preserve the species. This is a general picture of the plot of the game.