I was thinking that the game is set up in such a way that it might be relatively easy to add a new mode that offers a little more direction and more consistent challenge than the campaign mode, but is more involved strategically than the simulation mode.
My idea is that there would be a faction battle mode where the player selects a faction (Which would be the difficulty level) and fights several escalating battles with them. In between the battles, the player can use funds to buy their fleet, assign their perks (Which would be different from the campaign), and make some strategic decisions that may affect what ships they have access to purchase or how their economy looks. Each faction they battle might also have special gimmicks, and as they unlock higher difficulty factions to fight, the strategic choices they have to make regarding perks and other things would grow more complex. When they are defeated in battle, they have to start the faction battle over again from scratch.
For an example of how this would work, players would start out being able to faction battle against the Pirates, which would be the easy faction. The gimmick of the Pirates would be that after 75% of their fleet is defeated, they begin to retreat, but every ship destroyed gives extra money for the player to spend on buying their fleet in between battles.
The player would have a "planet" where they could slot in buildings in between missions against the pirates, making trade-offs between enlarging their fleet to help them in the next mission or instead buying buildings to unlock access to other ships to purchase or buying economic buildings that will produce more money after every mission.
After progressing a certain amount through the Pirate faction battle missions, the player would unlock the next faction (Maybe the Luddite Church), where they'd have more decisions to make, a different gimmick to deal with, and showcasing different ships that they have to fight instead of the Pirates ones.
What do you guys think? Interesting idea that could fit in well using the existing structure of Starsector, or terrible and boring?