In what way is it dodgy?
Here's the link to the official Apple documentation on implementing iCloud into apps - https://developer.apple.com/library/con ... ction.html - it doesn't get any more official than Apple's own development library documentation. If it's in there, it's official. These are the very guidelines they insist on people using and if you implemented it and they queried it, you could simply refer them back to their own documentation.
As mentioned on that page, you can use "iCloud document storage for user-visible file-based information such as word-processing documents, drawings, and complex app state.". As you can see, this has been specifically designed to do exactly what it is we're requesting.
This is no more "dodgy" than using the C: drive on a Windows machine for document storage.