Question stated. Command line parameters would be extremely helpful when the changes are order-sensitive (don't want to manually check the order of playlist) and when there are a lots of files (don't want the long loading time for GUI). I just wonder about why command line option is not planned...
[newest foobar2000 does not support TXXX frames and delete all my TXXX frames when I change anything via command line! Other command line tools (hard to find in any rate) either does not support TXXX frames or unicode or some other things. ]