I would personally want the backspace/delete key to work unmodified (i.e. without cmd, fn, or other modifier keys) for this particular function. Consider the fact that deleting photos in iPhoto uses only the unmodified delete key, and deleting songs from lists in iTunes similarly uses only the unmodified delete key. Inkscape (admittedly not an Apple software, though perhaps close to the flavor of your application) also uses the unmodified delete for removing selected elements of a drawing.
Here is a random reference I found, but haven't thoroughly read:
This indicates that a delete menu item is expected to exist which "Removes selected data without storing the selection on the Clipboard." Furthermore, "Choosing Delete is the equivalent of pressing the Delete key or the Clear key."