In our modpack HorizonSurvival we have added many new survival mechanics. The mechanics we have are
Thirst - Simply thirst thirst
Temperature - You could Freeze and overheat to death
Player Limbs - You could break your legs and get debuffs such as slowness or break your arms and get mining fatuige
Nutrition - You have to balance your diet because else you'll get debuffs
Thin air - If you go under Y-0 you will start suffocating
Seasons - Some crops you can only grow in some seasons