According to Thurrott.com:
Thanks to a leaked build last week, it looks like Microsoft is preparing to offer an improved backup solution that will give you better control of the items that are stored in the cloud service. As you can see from the screenshot above from build 14278, you will soon have the ability to turn off and on having Onedrive store your apps, passwords, settings and accounts.
The leaked build does not have the ability to completely backup a PC's drive to OneDrive, but it's possible it could be added sometime in the future. Again, this feature showed up in a leaked build of Windows 10. The current Insider version of Windows 10, build 14291, does not have these new OneDrive options.
Update. Those new OneDrive options appeared in Windows 10 build 14267.