Yeah that would be interesting or cool. Maybe even a 5th boss battle with arcane abilities or a mythic enemy that usually uses arcane. There haven't been enemies that use arcane attacks tbh. Or just a mythic arcane enemy that acts as a challenging boss with the orbit skill but not too challenging and it doesn't happen too much. A nerfed version of player orbit skill from the mythic enemies but still activates sometimes.
The arcane boss battle though could have a variety of abilities but what would be the name? We already have Ignis, Malum angus , Nix Gigas and Ignis . Maybe a name such as Astral or Aether with some name. The boss could be a summoner type with the staff casting arcane bolts and arcane orbits .