All purchases have been downloaded for this Apple ID
This is not possible at this time. On iTunes for Windows, as of version 12.2, you can choose to automatically download all music, books, and apps. On iTunes for Mac, you can automatically download music and apps; and defer to the iBooks app to automatically download books. Movies, however, is not available on either platform.

You can automate it using Automator, however. Your Automator flow would look like this: Open iTunes, click Movies, My Movies, then press Command–A, Right-click on the selection, and choosing Make available offline, close the iTunes window. (Based on this.) You would then have to schedule the Automator flow to run at 02 am every night or something. Doable, but inelegant.