So here's the start of an idea.  Would love to hear thoughts on this.

Hell. A small town wakes up feeling amazing and finds itself in a giant sphere of white. Curious, some people try going outside and never come back. Little by little they'll learn there's hell and devils outside. So of course they decide to stay inside for as long as they can. This isn't long because as the years go by the dome becomes more see-through and demons start entering.

So the story will be similar to Dante's inferno in that they're traveling through hell and trying to find their way out or into heaven.

There are three separate power systems I've been thinking of for this one.

Edens-the dome the cast wakes up in. These domes increase a person's stats and rapidly heal disease, sickness, and stamina. They keep out demonic entities. The problem is they don't last long in hell, and as time goes on they lose power, become dimmer which decreases their effect and allows for larger and larger demons to enter.

Grace-Infusions of personal energy.  These abilities would be color-based, similar to haki from One Piece. The characters will be able to infuse their Grace around themselves or into objects. The effect will be different based on the color. For example blue would be cold and red would create extreme heat. The colors will be combined for new effects.

Need to figure out what the core color abilities will be (Yellow, Red, Blue, Black and white) and the results that come from mixing the different Graces

The final system is a cross between devil fruits and zanpakuto, spirit seeds. Where a person is able to devour a gem that will bond a spiritual parasite to their soul. The entity will start off granting a simple ability like devil fruits but as the user grows they'll unlock forms and abilities like zanpakutos.
There'll be four kinds of spiritual seeds:
Demon-transforms the user's body
Angel-Grants the user a guardian that they can summon
REaper-The spiritual entity takes the form of a weapon or item
King-Creates a special field or area of effect

Also, I'm thinking certain spirit forms will be incompatible with certain colors like demons won't be able to use the white color of light and holiness.