Some simple enhanced toxins rules for more potent Toxic traits, where you don't want to use the rules from the GM screen, which you might only want to use for a single special badguy but need some enhanced toxins as the PC's start to get more powerful.

The Toxic trait stays the same, effectively becoming Toxic 0. For weapons with Toxic 1 and higher the Toxic number is the number of stages of increased difficulty on the toughness roll to resist the effects. In additional it is the number of turns after the after the original attack. That the user has to re-make the same resistance test with the same penalties, each failure inflicts a 1d10 points of damage that bypass armour and toughness as normal.

Example: Acolyte Sebastian is bitten by a visciously poisonous creature while investigating a feral world. The creature manages to penetrate the acolytes feeble armour and toughness with an attack and has the Toxic 1 trait. The Sabastians Toughness is 55 for resisting poison, he must pass a test by rolling 45 or below or take 1d10 damage that ignores armour and toughness. In addition next turn, regardless of whether he is attacked again or if he passes the initial test, he must make another test at 45 or below or take an additional 1d10 damage ignoring armour and toughness.

If someone can reach the an effected person they can use a full action to make a Challenging medicae test to stop that dose of poison affecting them any further. (optional, mediacae tests are affected by the Toxins modifier).

Obviously these rules start to get very deadly very quickly. A Toxin 1 could potentially kill someone. But it might become especially appropriate for enemies, trap, or creatures that rely entirely on the toxic damage.

Creatures such as small snakes, scorpions or weapons such as the hypo spray where the attacks themselves might cause a maximum of 1 point of damage but the toxin it's self is deadly if not dealt with.

Also anti-toxins, and their quick use, might become vital in some encounters with particularly virilantly toxic foes.

I think this sounds nice. However, you may run into a problem where the party is either overprepared or woefully underprepared. In the first case, your cleverly devised toxic traps and such will be for naught, making it tough to balance encounters and in the second case you may have some unfortunate party deaths on your hands.

Perhaps you could add something like most toxins cause unconsciousness instead of death, at least initially. So, player X is bitten by snakes, fails rolls or whatever and takes 20 toxic damage. He's in crit wounds and so falls unconscious (at 10 crit maybe? or at 5?). The player is now in shock. If he is not treated by anti-toxins within Y hours (Y = 10 - T# (toxic level)) then he dies.

Gives your players some leeway if they forget to bring anti-toxins or fail rolls spectacularly, without just outright killing them.