I've always had this scenario play through in my head for a long time as a what if some day Soma was forced into going back through the real castle, with a very dangerous guy trying to claim the throne as the successor of Dracula. However, the castle is trying to kill Soma as a human bit by bit and restore him to his might, recognising him as the true master, returned. Soma finds himself fully regaining his old memories as he traverses the castle. In the end, Soma, not far off of dying (as he has been gradually) decides, at the epic climax, that he *has* to retake up his old mantle in order to stop this really unpleasant fellow (who turns out to be the reincarnatoon of Walter) from becoming the new dark lord. He knows that he has no other choice, as little as he wants to. One thought which was playing through my head, although it does sound horribly cheesy, that as a result of his taking the throne willingly, before he's killed outright, it allows him a measure of control of being able to choose between being a vampire or a quasi-human/dhampir-like being, at any moment. However, he asks Alucard (who he's recognised through his guise as Genya) to help put him under a seal, so that he cannot misuse the full extent of his powers.
Yes, I know that this has some parallels to bits of LoS 2. I was amused by this as I played through it, thinking 'Hey, I thought of something like that!'.