- Simplified Judges Guild approach to poisons (hit dice of poisonous creature = damage per round and number of rounds of effect, delayed for 10 - HD rounds, default effect is sickness.)
- Save means half damage and no sickness.
- Collecting or manufacturing poisons for later use requires d6 situation roll to avoid accidental self-poisoning (except for alchemist, witch, or assassin.)
- Poisons last 1 week and cost at least 100 gp/HD equivalent.
- If a creature struck by an envenomed weapon makes the first save, the venom has worn off or been wiped off and won't affect anyone else.
- Social reactions are varied and can't be generalized.
Those are pretty simple rules that won't require much fiddling. Bookkeeping is limited to writing a HD number next to any poisoned weapon and erasing it at the end of an adventure. Rule #4 seems like a good general guideline for lots of things. How long do standard rations last? One week. It means that if you are adventuring every week, you envenom weapons and buy new standard rations. If you don't, you don't have access to either while in the dungeon. Rule #5 eliminates the need to track how many times you can use an envenomed weapon. Rule #6 eliminates situations where NPCs have "poison ESP" or unfair rulings to keep players from using poisons "just because". Rule #3 gives a limited special ability to certain classes, but I wouldn't go any farther than that to tie poisons to class abilities, nor would I specify how many weapons can be envenomed on a per level or per class basis.
I also stripped out the different effects for poisons and just made sickness the default. Maybe large creatures would have half action instead of sickness, and giant creatures would only have half move. Specific poisons might be given unusual effects, but these would be indicated in monster or item descriptions (4 HD paralytic poison, 7 HD coma poison.) One thing I might consider changing is: if a creature has a hit point bonus, add that to the damage bonus, but not to the number of rounds. So, 5 HD poisons take effect after 5 rounds and cause 5 points of damage per round for 5 rounds, but a 5+1 HD poison does 6 points/round for 5 rounds.