instead of showing a meter the character could gradually start to suffer from effects and it is up to the player to recognize what needs to be taken care of and when. No big, bright signs popping up on screen to tell you to eat/sleep/drink. That way it is not intrusive and can creep up on the player to cause something undesirable to occur....
Then you run into the problem of player simply using food every other time they enter their inventory just to drive off hunger. Even a limit on food eaten (the character might get bloated from eating too much, or waterlogged from drinking too much), if you paced yourself properly it would never be an issue.
Like I said in my quoted post, the LARGEST problem with ANY sort of "hardcoe" mode is that the real reasons that food/water/sleep/warmth are so pressing is because they're ALWAYS an issue. Even getting hungry with no meter or icon to tell you is not an issue once a player catches on. Once the player gets used to it, they will eat in intervals, completely illuminating the need for food. Warmth would most likely never appear in a hardcoe mode because its such a binary thing due to the way clothing most likely works. In real life, I can put on twenty t-shirts, but in a game like Oblivion, I can only wear one piece of clothing in one slot. Once you reach the warmth required, the problem has been solved. And, going further, the game is obviously not going to simulate sweat freezing, so that isn't a problem, whereas in real life sweating in a freezing environment is a CONSTANT danger that must be thought of when doing any action.
It simply comes down the nature of video
games, emphasis on games. Without a dedicated GM looking over every players shoulders, games rarely, if ever, accurately depict what survival is really like. In a game of DnD, a DM can tell you that your sweat is freezing and that you might want to pace yourself better, but in a video game? Its just too binary. You're either cold, or you aren't. Hungry or not. Thirsty or not. Its so much work to represent hunger, thirst, or warmth in a realistic manner you eventually find yourself making an entirely new game.
At the very least, however, I think simple survival mechanisms can be done well. For example, in Farcry 2, the player must sometimes stop for quite some time in order to put bandages on wounds and the like. THAT is where the danger comes from; when an action actually takes TIME and EFFORT. I can't just stop in the middle of the desert and immediately finish a meal and then go on my way; no, I have to stop, sit down, open the can, drop my weapon, start eating, watch for danger, keep eating, watch for danger, pace myself because I don't want to get sick, find a shady place so I won't get hot, make sure I ration myself, watch for danger, and so on. Emphasis on watching for danger.
But as I said, this is a video GAME, and we can't have the player stopping for ten minutes just to eat, because, unless the game is really, really into detail, with tigers stalking you through your entire meal, its not very exhilarating. However, even an attempt at making a realistic option seem SOMEWHAT more realistic than other attempts is good enough. In real life it may take 30 minutes to dress a wound, but Farcry 2's ten or twenty seconds works well as a stand in, being long enough to represent the danger of dressing a wound in a warzone, while being short enough to not "waste" the players time. Perhaps potions could take 5 seconds to chug in hardcoe mode so players would have to think before they spam potions. Little efforts like that can make all the difference.