I can force the game to add a specific item to the dungeon by dropping all my items except the one I want just before dying.
It is very easy to do, because the drop command is not a turn action.

Yep! true that. 

On next updates I will let the player witch item to drop, but for now you can use this method if you wanna populate the dungeon with useful items :P

Perhaps to prevent abuse you could limit the amount of items per player per floor to 1-3 at a maximum. You can however replace them, each time swapping out the oldest item.