Update December 24:
Hello everyone! Thank you for all of the kind comments, and suggestions! I've updated with another picture to clarify: there is still a litter pan inside the chest which I clean every other day. There is no odor so long as the girls cover their business, and I change the litter completely once a month. They still kick litter around the opening, but I put a rug outside the box and can easily sweep it up. Compared to the previous routine of mess in the bathroom and litter in the tub, I highly recommend it as an alternative!
We're going on several months here, and no spraying or accidents outside the litter pan. Anyone who comes to visit has no idea what is inside, which was the main goal! Good luck with your own projects!