This is a suggestion to add a new dimension with the 1.16 custom dimensions possibility. You could add a world in which it's similar to the overworld, but with a slight haze. (If that's possible) Now I don't know how this would work, but there are certainly tutorials on youtube about how to make a custom dimension. Once you make that dimension, you could code in a new type of world generation possibly. Having the spirit portals be at the middle of the most northern border and the middle of the most southern border of the world(the blue shiny thing). I know this is a bit scattered, but I don't have a full idea yet, it's just a concept at the moment.