Ah, I misread. I think you could make a game event that removes items from the backpack on death easy enough. Maybe something like:
<action_sequence name="clear_backpack"> <property name="action_type" value="Game" /> <action class="RemoveItems"> <property name="items_location" value="Backpack" /> </action> </action_sequence>
Just add a small effect_group to something like buffStatusCheck01 with a CallGameEvent trigger when you die. Totally untested but seems like it should work.