Rather than have a Samurai I would rather have Red Mage, Blue Mage, Geomancer, and BeastMaster.

BeastMaster could be a melee DPS that also controls all varieties of monsters as pets from Behemoths to little birds and everything in between.
Geomancer could take the offensive spells of the Conjurer to the next level and play something akin to an Elemental Shaman from WoW - Earthquakes, Stone 4, Wind 4, Water attacks, etc...
Red Mage could be a true hybrid - much like tank stances. a "Ranged" magic stance or a "Melee" physical stance or something. Or perhaps they could do something truly unique and make it so they can use it all whenever.
Blue Mage of course would use interesting monster themed abilities - Thousand Needles for AOE etc.. Perhaps to spice things up they could play something like a Druid from WoW or Udyr from LoL taking on specific animal or monster traits...