I've seen a lot of hunger, thirst, fatigue mods and many of them are really in your face with they way they're implemented. Like requiring you to sit at a table with a plate, fork and knife to eat and then punishing you harshly when you don't.
And this is why relegating it to a "hardcoe mode" is a terrible idea. It'll be that, instead of something functional.
Hunger and fatigue have important ramifications as actual gameplay mechanics. I've typed this essay a dozen times and I don't feel like repeating all of it just now, but the short version is that they make the passage of time really matter, which is the important balance point missing from the classic TES "practice your skills" method of character advancement. If there's a tangible cost for autorunning in a corner and casting spells on yourself, you're more likely to go run through a dungeon casting spells at enemies instead.
But thirst is mechanically redundant to hunger, and placing stringent restrictions on HOW you can eat and WHERE you can sleep turns it into micromanagement and busywork. Some people like the deeper simulation and THAT should be optional (if not, it'll be modded in anyway), but unless Skyrim uses an XP-based advancement system, I think a lightweight but still penalty-based eat/sleep mechanic is important to create urgency, improve the game's pacing and reduce the cheesy grind factor.