I'm actually quite pleased with the plot development. It might be overwrought and cliched, but if it seems cliched its largely because of how so much of western narrative is indebted to patterns of the monomyth. Very few people call George Lucas out on this, however much they may hate the Star Wars prequels. Just because it's familiar doesn't mean that it isn't effective. It's really a matter of execution.
If I'm being completely frank, which Sam Adams number three tells me I should be, I don't quite get the fetish of surprise. If a story is crafted well - and whether or not the LoS sub-univerise is well-crafted is, admittedly, a matter of taste - then "predictability" shouldn't matter. If surprise were all that mattered, then I would never feel the need to replay a game or reread a book or rewatch a film. For better or worse, MS seems intent on tapping into a familiar but effective narrative tradition.
Although I'm the first to admit that there was a jarring disconnect between the narration of the chapter introductions and the cutscene content in LoS, they were pretty intent on making Dracula a classically tragic hero, and I think they succeeded without the Deus Ex Machina that was the Crimson Stone in LoI. (For the record, LoI is one of my favorite CV games, but still...). For my money, Mercury Stream took what was just window dressing in the classic timeline - Christian iconography - and turned into a full-bodied theme. This might be alienating, and again its execution might seem hamfisted if you don't buy it, but I liked it.
Within this context, then, the Trevor/Alucard connection, while "predictable," really serves their purposes both of establishing Dracula as a tragic figure and of reimagining central characters and relationships from the classic timeline. I can't comment on the gameplay - I have not played it yet, although the framerate problems of the demo really don't register for me - but the plot seems to be moving in a satisfying direction. I don't personally care if it seems derivative, as long as it makes me care more about the character. For what it's worth, I actually find the narrative arc here far more satisfying than LoS, which still ranks as one of my favorite CV games behind CV4 and Ecclesia.
I should probably be working on my dissertation. Adieu. (Sadly, the Dracula chapter warranted exactly zero Castlevania references...)