A Metroidvania with Alucard as the/ one of the main characters. Perhaps something which shows him as he was prior to him turning white hat. One of the things I liked about Nocturne of Recollection is that it shows that he wasn't always a nice guy, and at the end of the day, he might be a nice guy for a dhampir, but he is still the son of Dracula. If Al were to be a full vampire in this, I'd have him much as he is as in LoS2, but without the scars. I'd love to see Trevor as imagined by Kojima feature, or something involving Leon's story, and tying that into the Sorrow arc games. Having Alucard feature as he looks in Kojima's style, and not looking under 20 is good, much like he does in the SotN art, or AoS. Al is inhumanly beautiful, and ageless, with a physical age hard to pinpoint, probably around late 20s or early 30s if pushed to guess, yet lacking the start of wrinkles.
I really liked the way that LoS handled his personality, in this respect, as well as loving his LoS2 redesign. He was still very hot imo, even with the scars. The castle would have the scope and more of the SotN castle. Ayami Kojima on board for the art, and Michiru Yamane for the music, in charge of a full orchestra. The soundtrack for the Pachislot games, it must be said, is at times nigh on perfect, in tracks such as Trezire de Spirit. The style would be darkly gothic, with elements of the castle as it is in SotN, LoI, and LoS1&2, as quite frankly the castle itself was stunning. If done in 3D, the animation would be of the standard used in the original cinematic trailer for LoS2, as that was insanely pretty. The castle looked stunning in that, what little of it we saw. If done in 2D, it would have the hand-drawn beauty of SotN, with today's available resources.
The game itself would be dark, fairly gritty, and grim, but with that wonderful dash of gothic romantic flair that I love in say, LoI. It wouldn't be afraid of using more mature themes, but it wouldn't be XXX rated in places just for the sake of being so. It would have the top notch standard of voice acting that LoS brought. I seriously adored Robert Carlyle as Gabriel, and Richard Madden as Alucard. I want a well written story that's able to make me sit on the edge of my seat as I follow the journey of the story unfolding, either celebrating in joyous moments, or in floods of tears like I was at Trevor's ending in MoF. I want to be able to connect with and care for the characters.
I don't know what studio I would entrust this to, as long as it was handled with the due care and passion it deserves. I would give the developers as long as is needed to make it, as long as it does get made, and I'd be all for programmers being allowed to add small touches here and there as was done in SotN.
I would love it to have an RPG basis, and feature some combo attacks, but have them be less of a focus than say in LoS. Long, hard to execute before interrupted combos can be a pain in the backside.
As a bonus bit of fun, I'd possibly get a good symphonic metal band to be involved in doing an accompanying theme song of sorts to feature in the credits, with a suiting music video in the bonus features. A band with the same sort of feel as Versailles, in songs such as Aristocrat's Symphony, Sonata Arctica, or some of Within Temptation's stuff.