A very general "everything welcome" brinstorming about what an emperor of some sort of a space empire can/should do? What are his daily routines what is his job?
Alternatively, you can note what he is not supposed to do.
It's for a strategy game that simulates a space emperor (rather then the space empire), so a game more from the point of view of the person, the emperor.
There is difference between empire and emperor.
The first is more used if some nation is apparently the most sucsesfull . Like kolonial sucses. Like the say the british empire. But it doesn't have a emperor. And it has a form democracy. But not directly ruled by the royal headfigure the king or queen. So its more a symbolic function.
A emperor rulez over it empire. More of a absolute ruler. So simulation of a emperor. Is more communicating with his advisors and military commanders. And anyone who directly reports to the emperor. Wich are a bunch of functions.He would see the space empire in a very high level of abstraction. And would only get lower if it was a very critical mission.
Then you have a choice, of what subgenre to go for. Political? Would fit more a non absolute ruled empire.
And political ath is not my choice and would go for that. But maybe others will.
So I would focus more on handling space empire from the point of view of the emperor. Communicating with his staf of commanders and advisors and special funcion like finance. Tech devision with education. You interact with NPC wich represent someting big.
Like communicating officer of commander runing a campain a war insome region of space. Head of militar technolegy. Top of security. Head of covert operation so critical mission and spying. Ministiry of defence. Also a command center where groups of military assets are representet in a iconic abstract way.
My opinion a emperor who rules the empire does so in a high level abstract way. Would not go into micro managing and command units far down the hiarchy of a battlegroup. A emperor can not multitask like a many 1000 core gpu. So he stick on desision wich go over the bigger picture of ruling empire. Also the empire does not do mission.
Like no ruling from a space fighter in battle. Wenn mobile it wouls be some flag ship battle star with a empirial command center department in it. The emperor controled that ship trough the commander or captain.
My guess is such game would be very AI heavy on different levels. A advisor is a AI agent like a ghost player who give hints or advise instead doing it self. Also option for cooperate play adviser with emperor.