Quests should complete themselves if you wait too long. Quests should "combine" - maybe you can kill two birds with one stone? Npc behavior should change over time. They should colaberate in unique ways. Maybe they decide not to offer a quest to you? Maybe Fg and Mg decide to team up? Maybe shop goes out of business?
I know it's a tall order but it would be awesome if the quests couldn't be "walked through" because there is no set way or set of ways they can go..: they are unpredictable.