Maybe I haven't been undersleeping enough then, I haven't quite noticed that much of a penalty.

I do think that it'd be more interesting, although quite a bit more work, if instead of dying from sleep deprivation, you had a chance to just fall asleep randomly after, say, 48 hours of being awake, with it causing various effects. As an example: you happen upon the blue-skinned woman after 60 hours without sleep. She tackles you, and you just shut down completely. You then either wake up far fuller than before, or just die from bursting, after she fills you far beyond what should be possible. Similar things could happen in the bunker, you could just fall asleep in there and wake up far more infected than before, or fall asleep in the pasture when resting, which could give way to another event, such as the woman finding you, or getting a trader encounter.