An option to prevent local caching of files, enabling/forcing OfB to behave more like a bookmarking function could benefit in some use-cases:
It's not uncommon for our userbase to misunderstand this aspect of OfB and treat a synced Document Library as set of bookmarks. Now that the syncing is much more robust, we see far fewer versioning/overwrite issues as a result of this, but they do still occur.
In an ideal world, we'd be able to set a flag at the Document Library/Site/Site Collection level that set a default behaviour of online-only (i.e. opening an online-only file doesn't cache a copy on the user's device - it simply acts a shortcut to the original in SharePoint). In a perfect world we'd also be able to decide whether the user could manually override this with the Always keep on this device function. I doubt it'll happen as it would drag even more complexity into an already confusing UX, and add complexity to the back end too, so I'd settle for this option being user-side in the OfB app.