As I don't know how to mod, but know the jest of it. I would like to express my idea as best I can. This would be a add-on like Dawnguard. I will start with the story then go into what I would like implemented in the add-on like Items, outfits themes and etc...

Story

Knights Of The Emerald Hand

A possible mod...

The Knights of the Emerald Hand Protected Skyrim and much of Tamriel from injustices for a short time in history. Until a great power Known as Parrallax. A yellow Dragon that inspires fear and steals the souls of the fearful. Storing these souls in a place similar to the soul carain where she feeds on their on going fears. Finding a way to banish the Emerald Hands remaining members to a place in between realms. only to inadvertently send her self to the center of Tamriel's crust.

Now as dragons have returned to Skyrim and Alduin reeks havoc on Tamriel. Parrallax has also found her way out and intends to take power through fear for her self. As the Dragonborn finds a place in the mountains southwest of Falkrith she/he discovers a valley with nothing but trees and some small lakes. Strange to the Dragonborn is a huge clearing between the trees. As the Dragonborn looks closer a huge green glass fortress appears out of no where becoming noticeable like a mirage disappearring. As the green fortress glows with green energy it disappears the same way it appeared.

The End.

There is more to the story, As you can tell I'm thinking of a Green Lantern theme with out using the Green Lantern symbols or rings. Instead the Knights use a gauntlet made of ebony steel and green glass armor with a green oval shaped emerald in the palm of the gauntlets hand that produces the energy known as willpower.

it would do any thing from summon a horse (green energy horse) to producing falling rocks (Also green energy) like the ones the Bandits try to drop on are heads. Anything in the game could be used as a construct as long as it comes from the green energy. Also when used stanima would be taped, not magika. Some perks could be programmed to accomadate like light armor tree or even heavy. There could even be a tree for the Knight of the Emerald Hand the Dragonborn became. The Idea is to find out how to free the other Knights of the Emerald Hand and together defeat Parallax in someway.

If you think this is a good Idea I have more content to share if some modders out there would like to take on this job. I can only offer Ideas you would have to translate into code or what ever. Or I could just write a story contianing the effects and looks to you...