Yeah a big game would be cool. I was thinking action is cool but I want to be doing it for a reason, not just lets blast some stuff and buy the way there is some plot too.
Maybe you should start with an inherited ship that can go not very far. You could use the ship for a couple of things cargo firstly you could buy a mining thing so you could mine minerals and sell them. You could buy a better gun and rent yourself out as a protector of local cargo shipments. You could become a trtader going between markets. Then as you progress you can specialise and get better equipment or become an alrounder.
So in the end you could run a protection buisness that protects trade routes or mines.
You could become a mining buisness which has to hire protection and traders to take stuff to market.
You could become a trader who takes stuff from market to market making money.
Or you could generalise yourself.
I would also like a way in which you could be corrupt, stelling money from others stelling the stuff you are trying to protect, killing mining places. Of course there are consequences (word get round, etc.). This would make the game play quite deep, I think (not sure though).
And as you get better you get access to better ships that first allow you to travel outside your vicinity then off world to the local solar system then to other solar systems.
You could win when you become of of the top 5% of people in the universe in monetry propety.
Sounds like it is a bit ambitious esp. because Tertris is the best thing I have programmed to this point and I didn't finish that. I guess this could be done in stages though. It is always fun to dream. Hmm, maybe we should have a think and cobble together some stuff we might need,