A Claymore site but not just be limited to women but men too. 

either a modern au genshin impact site or a genshin site which allows canons to be played (or at least canon face claims to be used for ocs) - preferably au to the actual plot so things don't have to be changed when new things come out that alter 'canon'

i've thrown around the idea of a genshin site that's also sort of panfandom and allows for other characters to arrive in teyvat similarly to the traveler, but that idea seemed too complex and confusing for my tired brain to logic out, plus i struggle to code

One Piece site centered around one island. Look, I get it. It's fun to be a pirate, and travel, and have your character search for the one piece, but it's just too big a scope for a roleplay to be wholly feasible. You could still get that pirate sailing the seven seas vibe by having missions revolve around trips to seek out treasure and all that.

A Gundam: Witch From Mercury site. It ticks a lot of boxes for RP, I'm surprised nobody has capitalised on the popularity yet! Academy setting, multiple external factions and school houses, slice of life aspects blended with the horrors of political manipulation, looming war, the ethics of technology, human-machine interface...Tons of powerful hooks!

digimon "humans trapped in the digital world and gotta survive while unfurling a greater plot, season 1 vibes" rp. I'm nostalgic af for that kinda thing.

Alchemy Stars pls....

A site where AI reads your posts and tries to figure out the setting of the thread so that it can join in and respond with little background details about what is going on around the characters in the thread. For example if we write that we are at a cafe it might generate a post about a waiter coming to ask us what we want to eat.

Someone pitch this to AI devs, I’m sure they’ll jump at the opportunity to make tens of dollars.

Sites that actually celebrate and reward high activity and posting more than once a month or like once every two weeks!

Seems like a lot of work for staff to have to keep up with weekly posting rewards, rewards that I feel would get old very quick for most members. 

I've seen sites run by a single staff member that could easily do this but allow me to specify since I fear people may not get what I mean:
Sites that celebrate activity over simply making activity checks (small awards, maybe bonus gold on site or something or little badges for activity I don't mean they have to do weekly awards they present on the week end). Too many sites have members sitting on their laurels posting once every two weeks to barely make activity checks that are lenient as all heck in a society that hordes faceclaims when allowed but that's just me and that's what I want to see!

A site set in the Darker Than Black world.