I think it would be good if bodies, such as monsters or people, began to decompose after a few days, and over a week, the bodies would disappear. This is assuming that no one has found them, like deep in a forest somewhere and not in a city. Retrieving meat from the bodies would be impossible as it could be labelled as "rotten meat" and so it means you have to gather it after you kill it before it starts to get off.
Regarding seasons, I think it would be interesting to implement. Say one season, certain food such as berries or crops start to grow and can only be gathered that season. I think this could be implemented in a hardcoe version of the game, or survival, where you have to eat and drink and have limited carry weight and healing over time etc... Anyway these are just a few ideas Ive thought of