I've been thinking a bit more about this recently. I've got some ideas for making the Amurites and Balseraphs more interesting, and more tweaks to the spell system.
Terraforming Spells: I don't think that terraforming spells in their current form are a good addition to the game. Being able to Spring whenever you want means you don't care about the downsides of settling in a desert, as you can just Spring everything to plains. This removes a layer of strategy from choosing where and when to settle. Terraforming also requires a lot of micro-management.
Without Spring, you can't have Scorch, as it would be unfair to Scorch your opponent's empire into desert without him having any way to fix it. Even if some counter-Scorch were put in, it's not good design to have some mechanic that requires your opponent to go out of his way to get the one specific counter for it.
I think Vitalize is fine, though, as by the time you get to archmages you're not likely to be settling much more, and upgrading your terrain isn't the most broken thing you can do at that point. The micromanagement burden is lessened relative to all the other stuff you're doing at that point in the game, though it could be reduced by having a mage take a few turns to Vitalize a 3x3 square of land, or even the entire BFC of a city. I've edited my post on spells to take this into account, but I'm now missing a few spells.
Amurites
This is a cross between the current Amurites and the Sidar. Mechanically, it's supposed to be a builder-style civ that fights more for defense and harassment than for conquest.
Unique Units: All the standard non-melee units are able to cast spells (see page 3 for more detail on the spell system). Melee units have aptitudes for particular mana types, but cannot use bronze, iron or mithril weapons (other units, such as Soldiers of Kilmorph, still can). "Affinity for X" means "+1 strength if you have at least one of resource X".
Axeman: Affinity for Nature, Shadow
Champion: Affinity for Nature, Shadow, Fire
Phalanx: Affinity for Nature, Shadow, Fire, Sun
Hunter: Summon Watcher
Ranger: Dispel Magic
Beastmaster: Cloak of Shadows
Archer: Wall of Stone
Longbowman: Living Armor
Crossbowman: Vitalize
Horseman: Rust
Horse Archer: Fireball
Knight: Cyclone
These spells have been chosen so that they are useful but aren't overpowered when spammed, encouraging the Amurites to diversify in their technology rather than focusing exclusively on either Bowyers or Arcane Lore.
Specialists: The Amurites get the Sidar bonuses to specialists and great people.
Wane: Wane works similarly to the Sidar spell, but it doesn't destroy the caster. However, the shade can only settle as a Shade great person, which gives +2

, +2

, +2

.
Hero: Govannon becomes available at Sorcery and starts with Channeling II. At Strength of Will, he is promoted to Channeling III.
Unique Buildings: Standard Amurite UBs.
Other: The Amurits start with an adept with Manipulation I (Inspiration), Earth I (Wall of Stone), Life I (Summon Watcher) instead of a warrior. This lets them help defend themselves a bit more easily and get a reasonably fast Shade, making up for some of their early-game weaknesses.
Balseraphs
Leaders: Perpentach (Insane), Keelyn (Arcane/Creative)
Loki: Can cast Inspiration (+2

, +1 Sage GPP) or Entertain (+2

, +1 Bard GPP). He can only have one of these active in a city at a time (though if an Adept casts Inspiration, he can have Entertain going simultaneously in the same city). He can explore rival territory and cities, but can't cast Disrupt. I just played a game as the Balseraphs, and it's crazy how much damage this little guy can do. I think he's much better served as a useful early-game support unit who can scout, help cities pop their borders, and get a little bit of research going.
Circus: Balseraph Carnival replacement. Gives +1

, +2 :culture, and +5%

per culture level of the city (i.e. 5% for poor, 10% for fledgling, 15% for developing, 20% for refined, 25% for influential, 30% for legendary).
Haunted Theater: Balseraph Theater replacement. Makes all Bards and Great Bards in this city produce an extra +2

as well as the normal Theater bonuses.
Freak: Cost reduced to 40

, Freak Show has a 30

cost.
Mimic/Harlequin: Unchanged.
Puppets: Arcane units can no longer use puppets.
Hero: The Puppet Master. Available at Arcane Lore. Archmage who can cast Summon Puppet (lasts 2 turns). This gives the Balseraphs a way to have fun with puppets without the tedious micromanagement of having two dozen units dealing with puppets all the time. Puppets can't use Domination, because that was really quite imbalanced. Summon Puppet is not doubled by Twincast.
Insane: Perpentach only. Causes your four traits to be randomly generated at the start of the game and changed at random intervals throughout. Causes Perpentach to make some decisions outside your control: declare war on other civs, give tribute to other civs, produce random buildings/units (they can't be canceled until they're finished), cause units to move around randomly, etc. All these decisions are things the player could do anyway. This gives the player an interesting challenge of trying to manage a civ where he's not fully in control. The downside should be balanced by getting twice the normal number of traits. Players who don't want to play the Balseraphs this way can choose Keelyn instead.
Overall: The theme of this Balseraph civilization is to make culture relevant beyond the 10 culture needed for a border pop. They have a whole bunch of ways to get extra culture, and Circus to make use of that culture. They can also do fun stuff with Freaks, Mimics, Harlequins and The Puppet Master.