Just merge the toilet break with eating and drinking, happening afterwards. That keeps the number of breaks the same, only making them slightly longer, and would make some sense too.
Yes, this was by and large my thought on the matter, as well.
In fact, I suggest going a step further, and making it so that players can optionally suggest to dwarves that they try to take care of all their needs at once, and possibly additionally altering the way in which dwarves track their hunger/thirst/sleep meters so that they can go up or down at different rates...
Basically, part of the problem is that a dwarf will go down to the bottom of a mine, get hungry just as he's about to start mining, run back up, eat, go back down, then get thirsty, run back up, drink, run back down, then get tired, go back up, sleep, go back down, decide it's time for a break after all that hard work, and go back up to slack off, go back down, hear about a cool party...
Thing is, you can make it so that they have a lower threshold they check when testing to see if they need a different break so they will also get a drink and go to sleep whenever they go to eat. Provided the player localizes all these things in a tight space, that saves time.
Then, you can add the toilets to be right next to the dining halls or food depots, and they can just run off to the restroom right after they take their drink.
Even if we're still somehow too squeemish to have actual bodily waste items, though, I still think it should at least be possible to have a "refuse" item generated any time food is consumed, not entirely unlike the way that seeds currently tend to litter the dining halls when you haven't kicked cooking into top gear. It may not require sewers, necessarily, but could still be used as fertilizer, and would at least be something to take its place in farming. Mass generation of such items would tend to lead to someone trying to build, say, minecart paths that functionally replace the "sewers", as well...