The possibility to make a batch job out of (for instance) multiple copy operations. 

Would be most useful for copying files from CDs and DVDs. Possibly other benefits too.

Assume you have many sundry files to copy from a DVD. These files are not sequentially ordered in the file list, so you cannot select them using Shift-click, and they are too numerous to use Ctrl-click (because selecting many files and accidentaly clicking without holding Ctrl invalidates the selection; it is all too easy to do, especially with laptops and confused mouse pads) 

I usually select a few files, and drag-drop them to the destination folder, which opens the file copy progress dialog. Then I turn back to selecting more files from the DVD file browser, while the computer copies the first file batch.

If I happen to finish selection files for the second batch before copying is complete (typical with large files!), and I drag-drop the new batch into target dir, a parallel copying operation starts. 

This starts thrashing the DVD and the two parallel copy processes run *much* slower than they would, if they had been started one after the other. Not to mention that now selecting and copying more files is tedious.

I propose that the file copying progress dialog be sensitive to drag and drop. Dragging and dropping files to the file copy progress dialog would enqueue a new file batch for copying. It would start the new batch only after the first one has completed. This way the entire file copying process is streamlined.

You may want to generalize this for other file operations. You may also want to drag a file copying window onto another, which would block one window until the other one has completed.

IIRC, the Eclipse IDE supports task queuing, so you may want to look at it for more detail.