AFAIK it is not possible to disable just the document library of the users' MySite. I guess it would be possible to remove the document library with a custom feature and feature stapling, but that would mean problems if at one point I would want to enable OneDrive again.
Right now I'm thinking to just hide all links to OneDrive for Business via CSS/JS as well as have an IIS redirect for the
personal/|username|/documents. That isn't pretty, but I can re-enable it at any time.
Disabling personal sites globally (i.e. remove the permission) doesn't help because then the newsfeed/following features don't really work.