Google-drive – get a business profile (and so VAT-less invoices – EU) for Google Drive without using G Suite

Giving edit access to Google Drive documents is sufficient. The way these files work, once they are shared with a user, the file will appear in their "Shared with me" list

If they remove or delete a file from this list, it will not remove the document from any other user's list, nor will it destroy the file. Only the owner can trash a document.

Learn more about trashing documents here: http://support.google.com/drive/bin/answer.py?hl=en&answer=2494934&p=restore_trash_collab

If the owner trashes a document, they can get it back from their Trash folder:

Learn how to recover a file or folder that you moved to the trash.

If something in Google Drive is moved to the trash, you'll see a warning and you may lose access to it at any time. Read one of the following sections to learn how to restore it to your Google Drive from the trash. When you restore something, it'll be recovered in Google Drive on the web, to the Google Drive folder on your computer, and to your mobile devices.

If the item is in a folder, you’ll need to restore the entire folder to recover any individual items inside of it.

Owners

If you're the owner of something and you’ve placed it in the trash, you'll see a warning that reads "This item is in your trash" when you open the doc or file.

If you’d like to restore a doc or file to your Google Drive:

Search for it in the Trash. Select the file(s) or doc(s) you’d like to recover. Click the Restore button.

Folders and file structures behave the same way, if regular editors remove these it will disappear from their "Shared with me" list but it only affects them, not the rest of the collaborators.

The gdoc and gsheet files are, as you've discovered, simply pointers to the online version(s) of the file(s). (This only happens if you have the Google Docs app on your PC or Mac, of course.)

The only way to make local backups of the files so that they contain your actual data would be to convert them to a different format. Converting a gdoc to a Word file and keeping it in the same directory would give you what you want, but converting files certainly isn't automatic.

Is it necessary, though? Google Drive/Docs is already keeping revision information, plus anything you delete goes to the "Trash" and doesn't get really deleted for 30 days (at least).

Of course, things might be a bit different for Google Apps. Certainly part of your agreement with Google is the ability to get to backups of your data in cases of vandalism/hacking/etc., no?

You might also look into the Data Liberation Front to see what data you can extract, although I don't know if that would be useful in your case.