Huge thread is huge XD
As Elrond is among my favorite heroes, I'd like to put my two cents in. I agree with Tiberius's original idea (first post), as he loses pretty much nothing of what he was and gains new, iconic abilities.
I really liked his original flood and the fact that it gets stronger as he levels up, (ike he's getting the hang of it XD) plus it's a really lore based iconic abilit of his, so it should stay.
On Elrond's advice it's the other way around, I think we should have some upgrades as he gains levels to show his knowledge expanding as time goes. Therefore on the level it's unlocked it should grant quarter of a level of xp and level 10 it should grant a full level. This would make a real difference between his beginning self and his former self.
This I approve, given that Rivendell's base is the studying and learning of ancient crafts and arts, it really fits here.
About the horse, I see no actual problem with him riding one, as one could think he patrols the borders of his land with his soldiers. Despite whatever role Imladrish might have among the other faction cavalry-wise, I believe Elrond would be fit to be able to ride, since he, just like Arwen, has been shown on horseback.
Also, one thing I always really liked about Elrond, was the fact that, unlike many other mounted Elves (except Thranduil) his steed is dark in color. Asfaloth (both Aren's and Glorfindel's XD) is a white stallion, and in AUJ too the guards rode steeds that were mostly white-gray, but Elrond's mount was dark brown, that perfectly fit his armor and hair color. Stupid point I know, but still, I really think it helps him stand out.
For the armor thing, I actually prefer the AUJ one, but since that's already implemented, that goes fine by me. The robe is fine, as it creates a theme with the other Elven Lords (Celeborn and Thranduil both start with robes, and later get Armor). As for the Dol Guldur armor, It would really fit his level 10, giving resistance to magic and a little stronger stats, just a little bit though. True, that would be yet another skin to work on and all that, but to be fair, Elrond has the most varied wardrobe we've seen among Elves (benefitting also for being among the most recurring characters right after Gandalf). Plus, once the player has Imladris's other troops all golden, he would seem...diminished with the brown armor. And it would be different from Thranduil, whose troops were colored in the bronze of sapling trees, but he himself wore a freaking silver piece (with Mithril elements it's speculated). So Elrond going from dark and silvery to golden would not really be out of place.
PS: I prefer Dol Guldur armor to Last Alliance, more elaborate and those freaking green pants! It's always a punch in the eye when I see them DX
I agree about the power of Vilya, as it fits perfectly. But I would add that the buildings in the base also get a passive repair that's a bit faster than the usual, which might be a bit much, but still, it's a level 10 ability we're talking about here. Lore accuracy has already be widely explained
Perhaps, though, this would downplay Narya...
But, I also go with The Necromancer0's Ring hero suggestion, especially the part where Vilya gets passive healing and goes Tornado! It fits with the One Ring part, and Ealendril said he's a mass slayer, so a tornado helps that.