Well, I want to give this a little push, so I'll post my ideas and maybe it can help.
Imladris in the lore, is the reclusive home of the Noldo in Midde Earth. Music, healing, knoweledge and the longing for the light of Aman are common themes in this faction.
I propose the next spellbook tree, with an straightforward offensive column and a more exclusive defensive column, centered in the concept of the sanctuaries. This rises from the fact that Rivendell is a sactuary for the good in middle earth, a place for travelers to rest and seek aid and a safe haven where relics, knoweledge and arts are preserved.
DEFFENSIVE:1- Sanctuary: Summons a sanctuary (that typical building seen in Rivendell that looks like an upside-down basket, with a small forest). The sanctuary can only be summoned near a player's building. It heals units near it and gives a long lasting exp adquiring buff to any traveler (heroe) that visits it. There's a max number of them
2- Luthien's song: The same, can only be casted near sanctuaries. Elves love singing in forests, it seems, and outside of the city (In the Valley, Ha! Ha!...........) and which could be a better place to hear the sound of Luthien than in a sacred place in a small forest?
3- White council (leftmost): But different for the old one, which doesn't work as far as I know. Summon heroes depending of the number of sanctuaries erected. More heroes or better ones as more sactuaries you have. Can only be summoned in a sanctuary. The succesive improvements in the sactuary aims for a high-commitment-high-reward choice for the player, as they have to protect the sanctuaries during the battle to get the best reward from this spell.
3- Light of Aman (right): Same as always.
4- Flood: A way is needed to make flood defensive, not related to sanctuaries, because you can reach it from the middle.
OFFENSIVE1- Horn/weapons of the Noldo: Buffs attack with long lasting effect
2- Breeze of Manwe
3left- Hobbits: For reducing the amount of summons in this tree, hobbits could become something related to the hobbit farms, like proposed by creso.
3right- Tom Bombadil
4- Las alliance
CENTEREvenstar, but with more emphasis to heroes near Arwen.
It's quite a change from the original concept, but Imladris is very centered in the knoweledge part right now and less centered in the travelers refuge and music haven that it is in my opinion. Also, we get rid of eagles!
Hope it helps, in any way possible.
Cheers to all!