Managing a large number of parallel iCloud accounts
iCloud is hard to manage in enterprise setting. Even with Apple's own macOS server it is hard to manage this kind of thing. A better environment would be Office365 or Google Apps. In both systems it's really easy to manage large numbers of accounts. And add content to for example contacts.

If you really want to stick to iCloud. Make an Automator action would be the solution.


Login to an account
Delete content
Upload new content
Repeat with next account


Further more I highly recommand to give feedback on this matter to Apple.