Stripe allows you to bill based on reported usage which seems considerably easier than crafting an equivalent feature from scratch. This is how we handle billing at skusavvy
I built a todo app that might interest you. It lets you nest todo items to any arbitrary level as I preferred it to the flatter trello structure especially when working with software projects that are very heirarchical in nature. It just stores data in local storage but you could easily mod it to import export json. Also has IDE inspired keyboard shortcuts for traversing the list. If you’re interested you can have the code it’s on my github.
But airbnb and uber were at a stage where they didn't have much to lose when they first challenged these regulations. Facebook is one of the most well known companies in the world.
Suprised no one has mentioned google scholar, the solution already exists. Not to mention google by itself is already a pretty great research tool if you know what you're looking for. You can even search by file type e.g. "cure for cancer filetype: pdf"