I dislike early reveals as an option, as it unfairly restricts the abilities of the village.
The witchhunt creator, Chocolate Pi, has spent years trying to address this type of issue in his games. Generally, there are three options:
1. A closed setup, with the rolenames either not being completely damning to the scum team or fake rolenames provided. There are flips on death.
2.A setup much like yours with something called soup. Soup allows either a member of the scum team or a third party to try to match roles to each players, killing them if they are right. The moment they guess wrong, the souping stops. You may make it so that the scum team has to give up their night kill for the night to soup or that they are revealed when they guess wrong. In this kind of setup, it's important to not have a flip on death, or the scumteam has too much information in endgame.
3.An open setup like yours, where all but a few roles are randomized between mafia and town. This is the closest to Witchhunt in its current form and what I recommend here. Every expect the seer (and maybe one other) will probably be able to prove that they have their role, but that doesn't make them town. Again, no flips on death are preferred, but the town should have a couple roles that can help them figure out what happened.
If you want to see that kind of setup done right, you can check this out:
Chocolate Pi Games