A third Joker would definitely be a copycat. Jeremiah is not a copycat since he’s completely different from Jerome and represents a different version of the Joker. With Jerome and Jeremiah, we’ve seen the two extremes of the Joker, so there’s nowhere new for them to go with a third Joker - they’d copy both Jerome andJeremiah. As to the two of them mixing and becoming the perfect Joker, we know from interviews with Cameron Monaghan and what we’ve seen of him in trailers that Jeremiah is naturally becoming more unhinged and thus naturally becoming more of a mixture of his own personality and Jerome’s, so there’s no need to bring a third Joker into the mix. And yes, Cameron mentioned the clone, but the producers themselves confirmed a while back that the Jerome laugh and ‘clone’ in the S2 finale were just meant as teasers for Jerome’s return in S3, to ease people’s concerns after they’d killed Jerome off in 2x03. They likely just hadn’t decided to have Jerome still dead in his S3 arc at that point. It’s much easier to just accept it as a continuity error than to introduce a third Joker in a season that’s got enough going on and way too many arcs and characters to wrap-up already.