I play on a dedicated server my friend bought, so honestly any mods made vanilla would be lovely.
The system Im hoping for the most is alchemy, because I think it would be really fun to brew different potions and remedies, but I feel like it might not be fully useful without some expansion to the health/damage systems.
I would love if injuries/aliments were added and expanded upon, to give us a reason to make healing items. Maybe capping damage across the board, but have it so any damage taken above the arbitrary cap may result in an injury, like bleeding, or a fractured bone. Could add sickness from hypothermia or heatstroke too, just a few problems that can arise when you misplay and get hurt.