My best idea would be a multiplayer. And there's 3 different ones
1. Freedom- Choosing a character to play as, you go around doing what ever you want (except hacking).
2. Roleplaying- I know this sounds nerdy, but there should be times where your character would be a Shopkeeper and you choose what you sell, like candy,kick me signs,etc.
3. Co-op- There should be this, though because you might need help when a person is attacking you. (There are totally different missions in this version.) So that you don't do a boss-fight unfairly.