That would be good for replacing jQuery and so on, but I would want to be able to replace inline scripts too sometimes. (And also some sites have their own copy of jQuery; I will still want to substitute my own if their own copy is otherwise unmodified.)
- External editor for textbox input
- Save form data to a local disk file
- Recall form data from a disk file (on the same or a different webpage than it was saved from)
- Replace scripts in the document
- Document/application mode switch
- Disable rich text editing
- Specify a remote filename when uploading files using forms