My thoughts:
Palpatine is a perfect Masterchief role, but since the cult killed JHT this turn, I doubt he/she could have been converted. While mechaerick was a cult leader, the cult would not have converted Zack, so unless he was in a pointlessly elaborate bussing operation, he/she was not converted then. Therefore, as suspicious as Zack's "network" is, he/she was not cultified recently. Could he/she have been somehow insiduous before? Yes, but a mix of scan and his effective scumhunting make that unlikely. Actually, there is a remote possibility that every cultist can kill or convert (perhaps with a probability attached) and Zack was converted, but that would be OP. My suspicion is this: Zack is a third party with one goal: To get the orb at all costs. Not inherently anti-town as giving himher the orb could be mutually benificial, or he/she may just blow up the planet...
I still don't like BL either. His/her PG confirms his roleclaim, but his/her logic is terrible and his/her desire for the orb is strange in the context of his role. That makes me think BL is a jester, especially since his power is after death. I have nothing against vidging him/her, but we have bigger fish to fry.
Specifically, vote: Topsecret, who is often much more active than this, but has hardly posted today, or in this game. Also, something about Mergle strikes me as slightly off, but not enough for a vote or a case... Just, I find his willingness to defend Zack strange and his statements about the killer in stormtrooper armor (instead of a stormtrooper) seem to be PIS.