Eh... If you're gonna have Stromguarde then I don't think you'd have much to do with the elves. The Forest Trolls, while they do have a few outposts in Arathi Highlands, are more centered around Lordaren and Quel'Thalas
Simultaniously I'm not sure if Sylvannas did much during the Second War, because I know that her sister has one hell of a hate for orcs and the bitch queen of the Undead appears to lack that. I also don't think that Antonidas did much at all either, due to him being mainly around Dalaran and this being more than 20 years before WC3, so I presume he was staying in there. Though he might have served as an archmage
But Khadgar should be playable. He was the apprentice of Medivh and convinced the Alliance to build Netherguarde after they defeated the Horde. He's far too important to not be in it
Oh, and with Lothar, you'll probably need to include the Stormwind refugees in there, because Lothar lead them all to safety
And Uther wouldn't be very minor, he was the person who set up the Order of the Silver Hand
As for your mage things, I'm pretty sure most Alliance mages use ice spells because they're the easiest to control. They don't use fire spells often due to them being dangerous or something. But I've NEVER seen a mage use a Lightning based spell at all, that seems reserved for shamans for some obscure reason. They tend to use Fire, Ice or just pure Arcane magic. Some arcane magic includes Polymorph, Arcane Missiles and Blink however