My thoughts were based on this really old niche game called "hard war" in the 90s where a player owns a ship and ferries goods between systems trying to make a profit in between. It gets complicated by the fact that there's rogue agents trying to kill you, cops trying to nab you when you ferry contraband etc.
My thought was to implement something like that with real functioning markets and planetwide events affecting commodity prices with hundreds of planets. It could even have some Stellaris like flavor where different kinds of planets have different resources they need to import just to survive. However I couldn't really figure out what the "fun" bit of game play would be beyond reading game generated news stories and trying to make a profit by running a trade route.
I had a couple of thoughts around putting in a mission tree somehow along with trade routes, automating trade routes and making it about competing corporations (ala medieval strategy games) but didn't get too far w.r.t. how the game mechanics actually work.
I'd love to see a repo if you have one already.