It seems poison weapon only works with Black Poisoning powder.
I have come across mushrooms in the underdark which are by all accounts poisonous and used for the famous drow sleeping poisons.
Is there currently a process for using these mushrooms to poison a weapon? If not could it be added? Could a new skill be created for create poison or some such.....Presuming it doesnt already exist?
I am sure certain items could be dropped in around the places, mushrooms and plants and the like that allow for the creation of various affect poisons...Sleeping, Sickness, disease, blindness etc. This would also make the use of bows a little more interesting.
Anyway...Just a thought