Add a new setting (default off): if enabled, when application loses focus - current file is saved, unless it's unnamed (wasn't yet saved). This is fully equivalent to calling File > Save manually.

Add corresponding menu item Save On Lose Focus under File > Read Only. When called, shows a similar dialog to File Change Notification except there are 2 radio buttons only: Don't save and Save. Reset if a new file is opened is also present (if checked - when new file is opened or created, sets Don't save automatically). When Save is active, that menu item displays a checkbox. It's generally similar to File Change Notification.

Also, rename item Read Only to Read-Only.