One of the main arguments (Probably the only excellent argument) against Undead Paladins is the fact that Paladins are immune to Undeath, and channeling the Light in that manner would be impossible. (It took a GREAT Necromancer to resurrect and control Sir Zeliek.) So. What if they got a great necromancer? The Forsaken have access to the power of the Val'Kir. I imagine that the Argent Dawn would have a problem with, say, the Forsaken going to Light's Hope Chapel and resurrecting all of those Paladins as Forsaken... BUT WHAT DO THE FORSAKEN CARE?! Raise them all! SLAY them all!! Down with Light's Hope as a Neutral party. Now that the Scourge in Lordaeron is less of a threat than it was, Forsaken Paladins can now aid the Banshee Queen in taking the rest of Lordaeron.
A group of gnomes, led by Narl Sparkly, went on a quest to find a rare gem which he has proven can be used to create his newest invention: The Incredible Aimright Arrow! It's an arrow that ALWAYS hits its intended target! (As long as it's pointed at its intended target) But! His team SHIPWRECKED! Stranded, they have to live off the land, and meet some Sand Gnomes. These sand gnomes teach them the art of survival, and insist that the Gnomeregan Gnomes stay with them on Tel'Abim. But, after a year or so, their ship was completed, and they sailed back to the Eastern Kingdoms. But! They brought friends! When you create a Gnome Hunter, you'll be trained by Narl Sparkley himself, and his Sand Gnome companion.
Blood Elf Druid:
A new academy is opened for botanists and arcanists. The Arcanists decide that "Y'know, we can like, manipulate these things, and nature magic in general, with our Arcane magic." And so it was.
Blood Elf Shaman:
"What else can we dominate with Arcane magic?"
*Turns Sunwell into Elementalwell*
"Look, Velen, I get what you're saying about Kil'Jaedin wanting to kill us all for not allying with the demons and all, but I'm just gunna y'know, summon some demons to fight the demons who are still chasing us after like 10,000 years if that's cool."
"We were here all along."
Dwarven and Human Druids:
"So were we."
(But for real. Wildhammer and Gilnean druids exist. ...Really.)
With the introduction of Sand Gnomes, some decide to teach their Dun Morogh brothers about the fact that fossil fuels actually damage Azeroth. Some, shocked by this knowledge, go full hippie and drop their arcane magic for Nature magic to make up for all the problems they've caused.
Same as Night Elves.
"We've been doing the same druidic thing for a really long time. What's this whole arcane thing about?"
Loa Priest puts on a plate helmet.
Medan, corrupted by Sargeras, goes to Mulgore and creates a new Dark Portal, to another world with new demons. Demons pour in and blast Mulgore until it resembles the Blasted Lands. It's surrounded by mountains, and far from the original, heaveily guarded Dark Portal; a perfect spot to stage an assault on Azeroth. Some Tauren are captured in this initial assault, and when freed, hate demons to the point of dominating them, using their magics against them, and torturing them. New faction: The Voodoomoomoos.