So my suggestions are in line with the relative power level of the new Warriors of Chaos book. Many things listed might incur an increase in points...
Part 1 - General Army stuff and Lords and Heroes
Terrain shifting Lore of the Old Ones would be excellent. Especially if things like impassable volcanoes are involved! A lore based on terrain manipulation/earthquakes would be really interesting and play a big role in the movement phase, which is a nice phase to control. A battle with a Slann with the Lore of the Old Ones will leave a mark on the battlefield, as new hills, pits, and jagged rocks appear, ravaging foe and landscape alike.
Spawnings: Will tie in to Oldbloods/Scarvets/skink chiefs and saurus/skinks.
Slann: I could definitely see Cupped Hands going away, but hopefully there will be some new in-built way for Slann to avoid miscasting or lessen its effects (above and beyond normal magic items/existing disciplines). Since Warriors lost the Infernal Puppet and Black Tongue, I'd be surprised if cupped hands makes the cut. I've always thought it would be cool if Slann got IF on two or more sixes, but only miscast on 3 or more sixes.
Slann starts at level 4, can be upgraded to level 5. No harm in dreaming big!
Some upgrade which allows the Slann to choose spells from up to two lores. If there isn't a Lore of the Old Ones, then this would be nice instead (or in addition). Maybe the default choice you make with Slann is either Loremaster of a single lore, or you choose spells from up to two books.
Oldblood/Scarvet - Ancient Tactics - A Saurus Oldblood or Scarvet, when joined to a unit composed entirely of saurus warriors/cold one cav/other saurus with the SAME spawning as his own, conveys the following benefits to the unit. (similar to tomb kings, but unit must match character's spawing)
Spawning A: Use Oldblood/Scarvet weapon skill
Spawning B: Use Oldblood/Scarvet Initiative
Spawning C: +2 A/+1 A
Spawning D: +2 S/+1 S
Spawning E: +2 T/+1 T
Spawning F: +2 M/+1 M
So this change might bump up the points for Oldbloods and Scarvets slightly, and also the spawnings would have a per model cost for the units. But how awesome this would be! Obviously it could be other things besides straight stat boosts, but the general idea is there. This gives a lot of freedom to take many different kinds of saurus of different spawnings, and would make a pretty viable alternative to the Slann.
Skink Priest - More lores would help. I think the idea of the Slann casting through the skink priest should be expanded to include all spell types. Maybe the #6 spell of the Lore of the Old ones is an ultra-devastating radial damage attack that you would obviously not want to cast centered on your Slann, but through a kamikaze flying skink priest. Hopefully the cloak of feathers remains as is.
EotG - The portent of warding is always in effect, at a 5+, 12".
Powers:
Focused warding - The portent of warding is strengthened to 4+, 18" until the start of the next magic phase.
Planar rift - One use only. The engine and any units within 6 inches of the engine become ethereal until the start of the next magic phase. While planar rift is active however, the portent of warding disappears completely.
Arcane Configuration - The skink priest riding the Engine of the Gods adds D3 to each of his casting rolls and D3 to his dispel rolls until the start of the next magic phase.
Burning Alignment - Same as before, change range to 2D6+3.
Blood of the Stegadon - The skink priest siphons some of the life force of the ancient stegadon to give to his comrades on the battlefield. The ancient stegadon carrying the Engine immediately suffers D3 wounds with no saves allowed. This augment can target any friendly unit within 12", and bestows upon them +1T for the rest of the game. This power cannot be used to raise the target unit's toughness above 6. Characters in units are affected, but only to a maximum toughness of 6.
So the EotG would likely stay 290 points. These new powers make it a force to be reckoned with, and it can be very versatile. The fact that it can create a small ethereal bubble means this becomes problematic
Skink Chief - Innate 6+ dodge save that is a ward save which can combine with other ward saves as normal.
Master of poisons - All of the skink chief's non-magical weapons have the poison 5+ rule. Additionally, when joined to skink units, all skinks in that unit receive the poisoned attacks special rule for their melee attacks. If the unit already has poisoned melee attacks, their melee attacks poison on a 5+ instead. But remember, you must be able to normally hit your target on a 5+ for this to work.
Or... you could also do the spawnings thing with the chief and skinks, giving them bonuses based on which spawning. Maybe something that boosts ballistic skill
