I not thin this is possible, but you can or teleport the player in this Dimension and then say it was a new World, or try to replace all structures, blocks, mobs, dimensions and biomes with your, but this was the same as reload the entire game, so let‘s say you go into the world, after 15 min (not for me, but here are players that it was so) you want to play minecraft, but then you re-need to wait, but this time 25 min (depends on what you want to add in your new Dimension). This is what i mean, if it was false so say it me.