Winter Horde with Cold Blasts is a neat idea. The upgrade visuals could just be cold aura effects added, although the unique special power (the one that Thugs have as Gang War) is hard to figure.
Red Caps is even tougher, because they're so melee focused. As someone mentions above, Archery could be a blast for it but it would be shared with Ninja.
Personally, I would love the use of the Apparition enemy group (the psionic ghosts found I think in First Ward). A Psionic MM pet set with Psychic Blasts I feel would be a good addition.
