Reinhart, (pretty good summary btw) yeah I mentioned this in another thread. I find it pretty interesting that the dates seem to be changing in Legends' favor. The biggest conflict was with Lisa's death, and that seems to be fixed now. The irony is that just when Legends seems to be able to fit into the timeline, Lords of Shadow is specifically said not to be part of it. D'oh! Oh well, can't win them all I suppose.
I think Alucard didn't so much rejoin Dracula as he was just hanging around. He explains his battle with Sonia as a test to see if she could actually beat Dracula. After he is defeated, Alucard says farewell, which I always took as him going into hibernation. That's why I assumed Trevor found him in the crypts. During Legends Alucard isn't only not physically strong enough to kill his father, but he's also not emotionally strong enough. It probably didn't help that he also just lost his mother. So between Legends and CV3, Alucard may not have been helping Dracula's forces, but he wasn't working against them either. They kind of hint at that in Symphony, when Death (or is it Librarian, I can't remember) asks him not to interfere if he isn't going to join them. By the time Trevor, Sypha, and Grant show up, I think Alucard sees there is a chance to defeat Dracula, so he joins them.
For Legends, I think they should just establish that Dracula was defeated, but not killed. Like in Adventure, it only appeared he was dead, but in actuality he escaped to build an army and declare war on humans and the church that attacked him first.
I do like the idea that after Lisa's death, he destroyed the village that killed her. When the church discovered this, they sent their soldiers to destroy him, thus escalating the conflict. That's how real wars usually start, small things turn into huge conflicts. It also gives Dracula a little more character and makes him less "evil", since he was just reacting to what happened.
The idea that Death might have had a role to play in Lisa's execution is also a good one. Not only would it fit the cyclical events of the Castlevania series, but it also makes what comes next even more tragic. And, if Death does reap souls, then the entire war is just good business for him. He's like the weapons dealer that sells to both sides.