Bloodborne

Something that I think contributed to the lightning in a bottle feeling of Bloodborne was the eldritch not-everything-is-as-it-seems setting, and I just loved going down down down into madness as you're battling these tough bosses and enemies. It'd be tough to nail that magic again... A different night of the hunt? Legends of a hunter that communed with the old ones? Became an old one?

Like you said, a bunch of other games have copied the asthetics of the first. To stand out, I think they should do something completely different. The cycle had repeated multiple times before, and will repeat again. They could do basically anything they want. I would prefer them to do something in the distant past or far future. The latter they'd need to come up with a reason why automatic weapons aren't ideal, but if 40K can use chainsaws and stuff, I don't see why a futuristic BB couldn't think of some lore reason.

I think Bloodborne + The Old Hunters are nearly perfect as their own self-contained thing, so my ideal would be a spiritual successor in a new setting but retaining some of the DNA of Bloodborne. It would be really difficult to replicate what they did with Bloodborne in any sequel or successor; the game was truly lightning in a bottle, like the first Star Wars movie.

That being said, if there's going to be a sequel set in the same world, exploring the old Pthumerian civ would be very cool and interesting.

I don't think Bloodborne should have any kind of direct sequel/prequel. A spiritual successor would be alright, but a big part of Souls games is exploring an alien-feeling world and slowly piecing together the background. We already know too much about the lovecraftian background stuff for it to have the same effect a second time. Miyazaki prefers to create fresh worlds each time too, and instead add references.

I liked the idea that Bloodborne was in the same world as the dark souls and sikiro universes.

So following that I think a good honest sequel would continue in the victorian/steampunk/France/London aesthetic. Keeping that concept contributed heavily to the whole Cthulhu aspect working so well.

But make it clear there are other supernatural forces. Maybe how each game cut out their own bubble of the world as an explanation of lore whatever.

My idea being that another elderitch being is attempting to warp the world of Bloodborne because we took out most of the major power holders already. I'd like to see a genuine power struggle from a power vacuum caused by our actions and choices but staying with that steampunk/horror vibe. a game that actually takes your winning character and forces you to fight against something strong enough to defend it's own realm against other threats.