Concerning the Belmont-relation-lineage-Sonia-retcon stuff:
At first I wasn't really a fan of the idea of the Belmonts having vampiric origins. It took away from the whole "Holy warrior(s) battling the worst of evil," so corrupting them with Vampirism was a bad idea in my mind and sullied the "tradition." Also, the fact that Legends plays out like the typical 90s anime of "forbidden love," and I know the game doesn't outright say that, but it alludes or subtly implies that Alucard and Sonia had a brief "fling" before she goes on to fight Dracula, thus resulting in Trevor and the Belmont's apparent superhuman capabilities.
Now with LoS, all the Belmonts are essentially "Alucards" that must defeat their great-great grandad because of their lineage. Dracula even says, referring to Simon, that "He is a Belmont. I cannot allow that bloodline to suffer any longer!" This struck me a certain way, because it shows Dracula/Gabriel might still have some remorse left in him. It's the "tragic irony, or poetic justice" scenario that's got me intruiged, which lead me to kinda understand Legends' approach despite all it's other flaws, and to understand those fans' reasoning for accepting that particular origin tale. Don't get me wrong, I also like the LoI origin for the "blood feud;" the idea of "Dracula in a prior life was comrades with a Belmont before things went sour" approach. I've learned to accept both origin tales, as it offers variety to the Castlevania brand. There are people that like "Elseworlds" stories; alternate beginnings/ideas to pre-established characters. Those familiar with comic books know exactly how this works. For instance, people may know Galactus as an ageless devourer of worlds. In a certain Elseworlds take, he became a RESTORER of destroyed worlds. It's just a different take, some find it interesting, others don't. But that's why we need variety, so people can discuss, compare and contrast the similarities and differences. This is what brings out some good discussions (so long as they don't turn into childish "THAT SOUNDS STUPID THERE'S ONLY 1 WAY TO DO IT ALL THE OTHERS SUCK" debates). Many people contribute ideas to three Castlevania brand, and as such, we should expect these varying origins. We don't have to always like what they come up with, but we don't always have to needlessly hate it either. Some may come off as more "fan-fictiony" than others, but it just is what it is
Perhaps the next "alternate" take would just use the original historical Vlad and have a disillusioned Belmont general from his royal guard betray him, and go on from there. Or make another "amalgam" Dracula like what MS did with Gabriel (Leon+Mathias=Gabriel, for those that are unaware).
Too Long;Didn't Read version: Variety is the spice of life. That's just my 2 cents. prunyuu~