Sometimes it is annoyinfg that LT works directly on an open file. To have a preview, he need to save it, and so the file is changed. If it worked in a temp directory with a copy of the file, then it could ask the user if he wants to save changes in the original file when quitting, if the user didn't already save it.
this has a additional advantage: it wuold not produce unwanted pdf - midi - eps - log files in the original directory.
This behaviour should of course be switchable on and off.