Hunger and Thirst system? Theres meat, farming and cooking this would be awesome!
Quality: The quality of metal and skill depends on what quality the tool you make is this effects the selling price and the stats of the weapon. Also repairing tools should be a skill and repairing tools will make the quality a bit lower so 5ql would go to 4.8ql etc. Also quality of structures like better quality makes them degrade slower.
Tools that rust when you have them out in the rain for too long. Just a mini feature!
Temperature? Your clothes can get wet in rain and it makes you cold. Also near campfire will make you warmer but you dont want to get a heatstroke!
Wearing clothes like fur keeps you warm in seasons like winter!
Seasons! To make the game look nice and effect when you can plant stuff like wheat in spring and summer and near end of summer then you cant plant them after that etc.
Merchants players can have to trade with other players!
Transport: Things like horses carts to carry big items over to build you home!
Able to get sick. Things like a cold so you get a bit ill and it effects your stamina etc
Hope you enjoyed reading!