This is is exactly what I thought Lords of Shadow was going to be, until Cox definitively debunked it in an interview. I would honestly be ok with this. But I would want it done right, if you are going to go back and do an alternate Castlevania 2, really lean into the aspects that fell away later, or ever immediately afterwards. I want it to be an epic monster mash with the Frazetta style fantasy look of the classic covers.
I would honestly prefer a minimalist reboot, somewhat in the style of something like Journey. Telling the story of Castlevania 1, no dialogue, no story to speak of beyond "You are Simon Belmont, heir of Belmont clan of vampire hunter. Dracula has returned, wield your ancestral whip, and kill him." Start us off in some woods, go through some mountains, maybe some caverns and graveyards, into the castle, kill Dracula. The end.
Some other ideas in here are pretty cool. Specifically like the idea of a fleeing Dracula ala Adventure. More immediate sequels means more games, and possibly more character development, depending on how they did it.