This is sort of like stretch goals but some things that I think would be interesting if they fit the game:
1) Long 'side' quest that help tell the history of the area and the nature of life.
2) Player behavior impact perception of common people. For example if a player performs evil deeds enough time (and there are witnesses) town member might hear of this and cringe when the player enter or evil people might ask the player to assassinate law-makers (mayor and such). Conversely if the player is known for good deeds a woman might need help finding her daughter or similar. There are variants on this but part of the aspect is that if the player is known to be strictly good an evil person might avoid them for fear that they would be turned in - this is slightly different than previous game in that often the player has a choice of how to handle a quest with disregard to the player known tendencies.
3) ability to dye/customize items
4) pets (non-combat pet that you have to protect when they get into trouble; and you feel very sad if they die

The same could be said for friend-ship with members of a town that you now defend not because they are good or evil but because they are your friend

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