I'd like to present an idea. Downloads should be controlled by bandwidth, not quantity.

You tell the file-sharing program it has X KB/s of bandwidth to use. You then add a handful of downloads to your queue, and the program begins downloading the first one. After a period of time (30-60 seconds?) for the download rate to stabilize, the program checks the current download speed to the total bandwidth, and if there is sufficient bandwidth left, it will begin another download. Repeat until X KB/s is used.

Does that make sense?