"You should be able to double click on an incomplete file and Limeware should automatically open and resume downloading the file."

YES! Please!

Better yet, have a setting where Limewire can search for incomplete files (during periods of inactivity?) and grab the ends of the files as it finds them.

But at least, if you double click on a file in the Incomplete folder, it should try to find the rest of it. Playing it at that point makes no sense.