I chatted with Prof on this, and we are not comfortable opening a twins loophole for Elsword character variations, for the same reason we wouldn't allow, say, the Adam West and Christian Bale versions of Batman to both be played. (Okay, that's an extreme example, but the point still stands.)

The big reason we don't want to allow this loophole even for characters with clear variations, is that it opens the game up to similar duos overall, diluting the 'one iteration per character' rule.