OneDrive should start with Files on Demand set to cloud only
After years of systems having more and more local storage, most new laptops and tablets now have much less storage. A 256GB drive is now on the high end. A user can have up to 1TB of OneDrive storage, which if it is downloaded locally, would easily fill the local storage and lock up the device.
Having each user that is set up on the computer start with all OneDrive folders in the cloud only would prevent this.
If the system detects the existence of a secondary drive or SD card, it should ask the user if they would like to use that for OneDrive storage. This could work like it did on Windows Mobile, where if there was an SD card, one was prompted for the location of new files, photos, programs, etc.. Since this was done on Windows Mobile, I cannot imagine it would be hard to implement in other versions of Windows.