Is it possible to send a container file as an attachment from the server in a script that runs overnight? And can one run the same script from a client computer to test it?

it is easy to do on your local computer but on the server you can not export field contents.  If the files are actually saved on  your drive and only a reference to them in the container you should be able to attach them, otherwise I would think you need some type of plugin.

You may want to look at the supercontainer by 360works they may have a way of doing this I too would like to hear other options on this subject.