Well I'v briefly looked through this topic, and enjoy the ideas of all mention so far, here's what I'd like to see without repeating what others have posted on here:
some sort of angel mage - main ability is flying, but has comparatively less mana generation but uses holy magic, also blessings which are enchantments that can only target friendly creatures
a daemon mage - similar to the angel mage but uses dark and fire magic, and have enchantments that target creatures that he can cast through, maybe with the curse type spells that's been floating around (curses could only target enemy creatures)
a sea based mage - sea creatures, would require converting the arena into a sea like terrain (zone at a time, specific spell or set of spells that flood a zone) gives all land creatures -2 combat penalty when in the sea zone, flyers unaffected, sea creatures would recieve a -3 penalty when fighting on land and not a sea zone, sea creatures would have less hit points due to weakish nature being water based life forms, however are cheaper to cast
a ranger - similar to the beast master but less creature intensive and more ranged attacks, maybe a basic ranged attack that gains +1 range to the attack to show their skill, spells would be bows, crossbows, magic arrows/bolts as an enchantment, as well as enchantments as traps etcetera.
and that's it so far, hope you enjoyed