Thanks for your inputs, they are quite timely.
iCloud can mean several different things but I'm assuming you mean iCloud drive here as a Dropbox alternative.
Initially in Foliobook 4 we believe can support single image imports from a variety of cloud services where the provider of that service has created the appropriate hooks. This will be on iPad Air 2 and iPad Pro, not sure about older iPads yet.
Later we'd like to support multiple downloads from iCloud drive, but after the new UX changes that you have referred to.
Are there plans to provide iCloud support? Not a critical thing (as I use Dropbox) but if you were looking to add Google Drive it may be a simple extension to add this as well?