Available Online Only - BUT... Windows 10 will delete your OneDrive files.
It is pretty easy to tell OneDrive that you want files only in the cloud. Just select the files/folders you need cloudified right-click and select "Make available online only".
That strikes me as "making it easy".
However, one word of caution if using Windows 10....
The Windows 10 OneDrive client has a fatal flaw that appears to result in it DELETING any files that it has trouble synchronizing. Even if they are marked as "Online only".
I have determined this to be the case after losing 300GB of files to the errant Windows 10 OneDrive client and eliminating all the possible causes until finally whittling it down to a system that I upgraded to Windows 10 recently - the only Windows 10 system syncing with my OneDrive.
In hindsight the culprit should have been immediately obvious since the loss of files started at the time that the Windows 10 upgrade on that system was completed.
Further, having switched to a 3rd party OneDrive client (syncDriver) it appears that there is some problem with OneDrive cloud access from Windows 10 generally which in turn is what was triggering the faulty "Delete files in case of sync error" behaviour, since even syncDriver is having trouble synchronizing some files.
However, since I have set syncDriver to sync in one direction only (cloud to client) it is not deleting the files on the cloud host. Neither is OneDrive deleting the files in the cloud itself. Hence I am 99.9% certain that the problem with spontaneously deleted files is due entirely to the Windows 10 OneDrive client.
The problem has seemingly disappeared since I disabled OneDrive on the Windows 10 client, even though it is still in use on various Windows 8.1 and Mac systems.