I could imagine a simple option in the Options Menu :
[x] Total Realism
Then a player would actually get tired (loosing concentration, focus and energy) resulting in lower mana, slower moves, faster stamina drain and not regaining 100% of stamina.
Solution : sleep in as good a bed as possible. A bedroll outside would only give 50% rest (meaning less time before getting tired again), while better beds (or moving in a cave or house) would increase it.
A new skill (Ranger) would increase rest from outside sleeping.
The player would also get thirsty and hungry resulting in less stamina and no health regain, and when VERY thirsty/hungry : starting to loose health and power for carrying.
Solution : Eat and drink.
The visuals could be a small mark on top of the already existing stamina/health bars, indicating how hungry/tired the player is.
VERY simple, yet soooo much more immersive/realistic.
It wouldnt take very long time to make. It wouldnt be very difficult to make. It wouldnt be "forced" upon the player as it would be as simple to turn on/off like Subtitles.
Sure, you might say, a modder will create this very soon, but I just prefer Bethesda (who already made such a great work putting the frames in place for it) "finished" the job.
Hell, if it was a DLC I would buy it, and I usually detest DLCs




