I'm not a Windows user per se (I use a mac.) So I'm not in the knowledge about user accounts for windows. I'm not too keen to make any suggestions which may muck up things or worse. Particularly when I don't know. lol

Let's look at it. Your LW preferences folder will go into each of your own username folders. So I'm not sure why you each couldn't set up a separate LW dwnld folder in a different location. The logic works. But in practice ... hope.
But you'd need to ensure that each of your dwnld folders are definitely in a different directory or sub-directory!!! (Because your incomplete folders will also be alongside each of your own dwnld folders.) Sounds good. If you're willing to try that out, get back & tell us how it goes.