There should be a mod where you have to upkeep things like hygiene; You have to eventually start showering, or you'll start attracting any nearby mobs (example;increasing detection radius) and it'll make your screen look a bit dirty. (sort of the same way pumpkins obstruct your vision a bit) and you'd need a toothbrush, or your mouth will get all disgusting and (maybe eventually) you will be unable to eat food until you can get your teeth brushed.
then there could be a toilet but there's really no point as that can't hurt you in any way except for hurting your ass
there could be different types of showers to increase efficiency, and you could just as well jump in a lake for a bath, but with less improvement
toothpaste could have maybe a few different things added to the world, such as (some toothpastes use seaweed extracts) seaweed, (i don't know how you'd get baking soda though, so this idea is a WIP.)