Systems like natural fatigue and such *are* realistic, and all that, but I'm unsure of how much they add to a given mod. They do a touch of realism, granted, but sometimes that might be more frustration than anything else. The way I see it, the original D&D rules were created specifically for playing with friends and, importantly, a DM, who work together to create a cohesive, sensible universe. The transition towards CRPG hasn't been kind to this, as I think there's something lost without DM interaction. In fact, I'd rather have *more* realistic implementations--starving, thirst, etc--in multi-player environments with DM support than without.
Seeing as how this project is, and always will be, single player, I don't want to simply add more time for the one player(as un-equipping armor, setting a fire and other such things would be). Now, as said before, I *encourage* other modders to have unique instances within their projects. Say, for instance, you're making a cave full of Cloakers. Perhaps, specific to this area and this area alone, being near a campfire is the only safe way to guarantee that the creatures don't attack(either while walking or resting). Great! This is interesting, unique and doesn't impede the campaign as a whole. Your work stands out, and yet we can have the standard systems that the player can fall back on and feel comfortable with.
SOZ is going to be the default, but variations, in the vein just described, is more than acceptable.