Ulrik,
A way, like with social media posts, to schedule uploads. Of course connected to snapshots so nothing will change.
Difficult to implement and have it be able to always succeed. Users could quit PM, or close the Contact Sheet, or change the selection, or move/rename/delete the photos prior to scheduled upload time. Any of those things would cause failure.
If we really wanted this to always succeed, then it would have to copy the images to a private place and have a separate process do the upload at the scheduled time. This would be a tremendous amount of work.
-Kirk