An All-or-Nothing Apple on iCloud: Is this a tough landmark?

Apple's documentation seems to consistently argue that user-created documents should either be saved locally or should be saved on iCloud. Here is one example from this iOS page (the emphasis on All belongs to them):

All application documents are stored either in the local sandbox or in the iCloud container directory. The user should not be able to select individual documents for storage in iCloud.

I would like to allow users to manage documents separately: perhaps they want one to be local (to save space from their iCloud permissions), the other must be in iCloud so that they can manipulate it on different devices, and the other in DropBox, so that they can copy it to a friend's account or create a backup manually or even modify it externally. The all-or-nothing approach will actually hinder flexibility, especially when I come to the DropBox sync view . In my case, individual selection also simplifies the user interface.

So the question is this: can I expect problems during the verification if I stick to my plans so that users can choose their storage preferences (local, iCloud and soon DropBox) for a separate document? I did not find specific recommendations for this. Edit : none of the guides even mention iCloud.