The masked Firefly seems like a strange choice for an Oscar-nominated actor, but Mad Hatter and Two-Face sound like suitable choices as well.
As mentioned, Hill has a range that can really justify any villain casting, though THR has said he’s mainly being eyed for Penguin or Riddler.
Really, any of the male Batman rogues could be on the table here, seeing as we don’t have an official breakdown of what villains will be appearing, but the remaining rumored options include Firefly, Two-Face, and Mad Hatter.