Um... Having read the trap and coating rules a little more closely in the packet and being a semi-recently approved Marshal for the Calgary chapter, I'm going to just weigh in on my thoughts re: coatings and weapon traps, and how I'd rule them if I was running a mod; if someone with more experience (or ARC, or an owner) says I'm wrong on this analysis, then I would probably take their word on it over mine.
Unless something is changing from 1.3, DiscOH is correct in that a weapon trap requires a weapon be supplied by the person who originally sets the trap, and that a coating can be applied.
In 1.3 it states that only the person who sets off the trap is hit, and coatings are used up after only one strike, so there are no issues regardless of whether you're hit by the trap or not.
In .10, weapon traps rely on a pivot point to determine who is hit (thus can hit multiple targets), and coatings last "until they connect". As a Marshal, I would probably rule that the coating affects only the first person hit by the trap who does not call a
Dodge,
Parry, or
Riposte against it, and all others hit would take the non-coating damage and effect. This sounds a bit odd, but if the idea behind these defenses is "you moved your body/weapon in such a way that the incoming thing didn't actually hit you", then, to me, the weapon didn't actually "connect" with the target, and so the coating is technically still on the weapon.
I'm fairly certain this is more of a oversight-in-wording loophole than the way they are supposed to interact, as the "until they connect" wording isn't used anywhere else in the playtest packet or 1.3 rulebook that I could find; all other similar things note that they can't be re-used or Meditated if a defense is called against them (including Parry, Riposte, and the various Shields), but based on what's written and with no other cases of "until they connect" that I could find, that would be my ruling at the time.
On the topic of Potion Coating, it's worth noting that they are delivered with the Spell qualifier, and so I would rule that they would affect the first target that didn't call a
Dodge as usual (Spell Cure Wounds 20, for example), but would pop a Spell Shield as usual before changing to whatever the trap's damage would have been without the Potion Coating against everyone else (who could then call
Parry and
Riposte against it, as it's now a weapon qualifier).
That's... fairly complicated to do, and I'm really unhappy with the ambiguity present in the unique wording of coatings in the packet now.