I think the most integral part of a witch trail is the paranoia, the ability to accuse someone who isn't really a witch.
I propose 1 additional skill, 1 small change to witchcraft, and 1 new buff for a witch trails.
The change to witchcraft would be there would be no drain in Providence, everywhere else in the light yes, but Providence no. It was thought that evil and decadence thrived in cities so that could be the justification for this change. This change is meant to encourage witches to come to Providence and cast spells.
Then comes the buff. Suspicion of Witchcraft. Everytime a witch casts a spell everyone within a certain radius gets the buff including the witch. This is a buff that fades over time in a perdictable manner, having outstanding scents of any sort slows the fading, being part of a town speeds it up a bit. Being a witch slows it down a lot. This also a compounding Buff, so a witch casts a lot of spells she will have a high Suspicion of Witchcraft, or if you have had a lot of witches cast spells near you you would have a high Suspicion of Witchcraft. Once the buff reaches a certain level, it shows visually on your character in some manner everyone can see if they are paying attention and no what to look for.
New Skill. He Who Casts the First Stone. This skill is only available to non-witches. But it allows the player to craft an item, which when right clicked on a character with high Suspicion of Witchcraft sends the them to the stocks for 24 hours.
At this time a community built Trail By Fire sign post is set up near the old tree in Providence. Think of the Santa Sled from the Xmas Event. In 24 hours it must be filled with enough objects to finish it or else the character accused of witchcraft will go free and the character who sent him there will be stocked for 24 hours as well. Of course this Trail by Fire would require a lot more items as well as at least 1 Evidence of Witchcraft to be completed.
Ideally this would encourage players to join towns, not commit crimes, be suspicious of everyone in Providence, send both innocents and witches to the stocks for witchcraft (but not without costs) and for players accused and accusing to come to the forums to appeal thier case (the Trail By Fire is set off by the Old Tree in the Lake so you kind of have to know what you're looking for) either to get people to add materials, or asking for people to not put materials in.
One last ammenedment would be some sort of structure that could be placed outside a witches base like a Trail by Combat that intiates this same sort of process.