A simple age old thing that I'm not sure people have even noticed.
The outhouse currently requires 200kg of dirt. With every dupe use 6.7kg of polluted dirt is added into the outhouse until the 15 uses are used, adding up to a 100kg of polluted dirt.
When you empty the outhouse, you only get the polluted dirt back, and you need to put 200kg of new dirt in there.
That is 200kg of precious dirt lost to nothingness every single time an outhouse is emptied, automatically or manually.
Now before anyone gets their panties in a twist and claims this is intended behaviour:
First of all. The dirt doesn't get converted. It just stays in the outhouse at 200kg until emptied and is then DELETED.
Second, if you look at the lavatory, every use uses 5kg of water, which when outputs 11.7kg of polluted water. That's exactly 6.7kg of additional polluted water that you get back.
Finally, if you deconstruct a full outhouse, you get back the polluted dirt and the dirt. To top it off, this is actually quicker than emptying too.
There's 2 options the way I see it:
Leave the dirt in the outhouse when emptying it, which is par to simply giving the outhouse 2 different types of materials when building it.
Or convert the dirt into polluted dirt by making every visit 20kg of polluted dirt. Possibly removing 13.3kg dirt (200/15) per visit to avoid exploits.
Seeing dirt is now used more often for farming, it has become a much more precious commodity, and simply deleting it is just wrong.