We've already discussed this, since a good majority of Wc3 RTS players have not/can not or no longer, play wow - they will be unable to follow the story.
I'm pretty certain WoW players aren't gonna jump off and buy sc2 just to play wc4 (the rts) either.
Haven't seen that in the thread, but I'm cool with it.
But your right the blood elves didn't worship Ashzara, they follow Illidan because he has promised to 'numb' the pain of their thirst for magic.
By leeching from demons. Goodie.
Anyways, regarding races I've come up with an idea, expanding on something that has been mentioned already. It's quite a flexible system based on "alliances" where the player picks a race at the start of the game (troll, gnome, human, dwarf, w/e) which will be the base of his or her "civilization" in the game and as it advances he or she can ally an X number of races that will grant access to a limited amount of units/spells/whatever of said race.
For example, at the start of the game I pick dwarves as my "main" race, giving me access to all of its buildings and units (let's say dwarves have the best siege engines of all races), and later I ally myself with Blood Elves, which will grant me a limited number of their units, tech and etc. (In this case, adding spellcaster units to my army). Furthermore, I could ally myself with another race, in this case Naga, which also grants me a limited access to their units and tech (let's say they have the best naval units in game).
So, once we have advanced quite into the game, I will have an army of dwarves supported by blood elven and naga units, with good siege engines, sorcerers and naval units.
Or I could have a dwarven army allied with humans and tauren. Or orcs and trolls. Whatever. The point is that each player could end up with an army made up exactly for him or her, focusing on an aspect with their main race with tints of others given by the "allied" races.
Obviously we should limit the system by following the lore. For example, night elves can't ally naga, so if you pick night elves as your main race or as your first ally, you will not be able to ally naga later.
Or humans with orcs, and so on (although I think we should make humans the most flexible race, capable of allying themselves with everyone else, we are cheap bitches indeed).
Whaddaya think? It breaks with the fixed race thingy we had in WC3, and it can be quite fun.