I've not read the whole thing yet, but I do have a couple of ideas for future factions.
1) The Terracotta Warriors. You know, those chinese man-size statues. I can imagine an army of constructs which aren't undead, aren't scary but are still controlled by one central mage or mages. It doesn't have to be Chinese-styled.
2) An all cavalry army: there are a few of these that turn up in history and fantasy-fiction.
3) Beastfriend: an army mostly consisting of animals, with a few human/elf/orc allies (a druid faction?) A step further than Ravenwood, but without the trees
Okay, the Terracotta army is arguably one of the coolest ideas I have heard yet on this forum. Even if the Terracotta warriors are just the uber-tough unit for a new faction styled on the Huns or some other Eastern concept army, I would love to have something like that hit the field! Excellent idea! Perhaps require them to have a mage unit in play in order to run them, and if the mage unit dies, they cease to fight. That would be an interesting twist there, too, and an interesting way to use mages in the game.
As for the all-cav army, the new High Elves faction actually covers this pretty well. With the new High Elves, you can have 4 units of Chariots as your Core choices, a unit of Knights, and a 2 units of Bowriders for 1970 points, which is a pretty respectable little faction. Of course, running a 7-unit army in 2000 points (especially ones with such short life-bars) is most likely suicide, it is the first time we have (legally) been able to run such a faction. I do think that it would be cool if Hawk Scouts got changed to a Core choice so we could do this with the Hawks, too...that'd be sweet. (Hint, Hint, YMG...)
I personally think your "Beastfriend" army would be a bit too Ravenwood-ish, but it would be pretty interesting to see... Is anybody else thinking that this sounds like the armies of Narnia?