I built this late 2019 for fun and thought it would make a nice product idea!
Lego hasn't had any medieval themes in the past few years, so I thought a medieval product idea would be great for all the castle fans! The build is supposed to be a watermill that is built into a dam, so the water comes from above the wheel instead of the waterwheel being partially submerged like normal. This aspect makes it more unique and gives off a neat vibe. The top of the dam is used as a walkway for the inhabitants of the town, and even has a boy fishing off the top of it. The dark orange trees as well the water provide some nice contrast to the olive green landscape. :)
A LEGO set like this would allow for some great details, such as the wet and mossy stone. It would also be a good opportunity to get some castle minifigures and possibly an animal or two (like a cow, horse, chickens, or even the return of the goats ;) ). Overall I think it could bring even more variety to the LEGO Ideas lineup!