Talk about a leading question... not only are you combining two different theories with the last one, but they both have a bunch of implied baggage attached that potentially contradict themes when combined.
The fact is that they are both equally plausible based on the hard evidence we have, but for all I know, Alucard is Simon's lost half brother from Mars.
However, due to storytelling and thematic reasons, I will say the latter as it doesn't add an otherwise redundant character to the LoS story.
The first Alucard has no point. Sure, it sounds just like the old Alucard, giving it more "credibility" in that regard, but that's just it: he'd be exactly the same as the old Alucard, and would add nothing to story. For one, LoS Trevor has taken the spot that Alucard used to fill. Melancholy son? Check. Shackled to mission by blood relation to father? Check. Partially motivated by thoughts of dead mother? Check. For two, Dracula doesn't need any more motivation in this. Original Dracula had one wife die to curse God, and another die to curse humanity. New Dracula doesn't need it. His humanity has been lost and corrupted by his vampiric and demonic powers, he's pissed off at God for screwing him over, and he's pissed off at the brotherhood and Zobek (and by extension humanity) for screwing him over too. A second wife would add nothing, and when you're limited to two more games, the last thing you want to add is filler characters.
The latter plot makes sense, as it doesn't throw away a perfectly good character (Trevor) just to replace him later with a character that serves all the same purposes in the same game. Again, this is a 20 hour game. Three unique stories and back stories is a bit much. And frankly, the latter plot actually uses the new plot devices and characters, as opposed to the former which really just appeals to a sense of sameness with the old canon.