All the other Divinity games have had classless character building, this one probably won't be different.
A Day/night and weather cycle sounds good, but the weather cycle is the least important part. It could make for interesting gameplay, if rain makes everything wet and susceptible to lightning and strong to fire.
I don't really agree with the idea of making it dark and impossible to see. What's the fun of that? Don't make it impossible to see without a torch, you can't sneak when carrying a torch.
Giving guards torches will also make sneaking difficult, unless you could cast rain to put the torches out (without alerting the guards.)
