If all you want is immersion, that hardly requires a special mode for the game. Just go eat, drink and sleep on your own.
I do. And I impose rules on myself too, like no eating or drinking potions when it would not actually be possible. But I would like for the game to demand these things. It helps with my immersion. For example. If I haven't slept in three days. I'd like to stagger a little when I walk, or fumble around. Perhaps the screen would become blurry. By the fifth day your on the verge of collapsing. That kind of thing. You cannot hold your shield up as well, etc., etc.