Artificer: Neurologist - An artificer that studies brains and the mind. A scientist that seeks to unlock the secrets of the mind and its true potential, psionics!
Bard: College of Wraithcalling - A summoner focused subclass. The basic idea is inspired by elden ring, when you kill an enemy or are around spirits you can try to persuade them to join you and you can summon them. Basically your a pokemon trainer collecting spirits.
Druid: Circle of the Abyss - what would happen if a druid is lost in the abyss or decides to explore the abyss? well this subclass is the result. The main feature will be able have the druid wildshape into demons, perhaps only demons (still working out the logistics). Another feature will be able to find portals.
Monk: Way of the Mind - what would happen if someone gifted with psionics would be trained as a monk. I am planning to make this monk a quarter caster. They will be able to pull and push creatures with their minds, use telekinesis. Think of what a githyanki and githzerai monk would be?
Paladin: Oath of Dragon - A paladin with draconic abilities that serves a dragon. The oath is sworn to that dragon. I want to have a bit more warlock feel to it.
Ranger: The Feral Stalker - A ranger that has chosen to exile themselves in the wilds as a result of contracting lycanthropy. A more feral ranger with some barbarian like abilities and maneuvers.
Sorcerer: The Poltergeist - A sorcerer that can find and talk to spirits and ghosts. It'll be the sorcerer version of the phantom rogue. Subclass abilities will allow you to posses creatures, travel into the into the ethereal plane, and even become a ghost. I have an ability in mind that will allow the sorcerer's soul to leave his body, travel in the ethereal plane to scout ahead.