So the cult as it stands is kinda underwhelming. They only have two pretty vanilla roles.
How about removing the cults conversion ability and giving them lots of deception-oriented roles? You could even move some of the Mafia Deception roles from the faction into the cult.

You could also add roles that read /change last wills, give fake feedback (a Drug Dealer), plus some weaker investigative roles oriented around finding power roles. The entire faction would change significantly if this were to happen.