The privacy and security part is not inspiring confidence. Scrolling to the next section got me thinking "Don't get scammed at closing, get scammed before closing after uploading your mortgage documents to a random website."
Cool idea though.
What sensitive data do you think is on a loan estimate? I've received a dozen over the years and it's literally just your name and the address of the property you want to buy. Both of which are public information if you do purchase the property.
As others have mentioned, title fraud. My recent closing disclosure has buyer, seller, agent, and title company. It'd be pretty easy to call the buyer claiming to be the title company and request a wire for exactly the right amount to a fraudulent location.
I'm skeptical anyone here has actually bought a house. That's not how it works at all.
Because every country has agreed on a standard procedure