To make a unit’s items droppable, FE7 checks a bit in the unit’s character data - meaning you need a separate character slot for a a unit that drops its last item. If you paste the following hex to 0x17826, the game will instead check to see if the unit has bit 0x40 set in AI Byte 4 in unit data, similar to FE8’s system. So if you wanted a unit to guard a tile (0x20) and drop its item, you’d set 0x60 as their AI byte 4.
201C4130007840210840000000000000