idea to make the deepslate renewable for that you have to put a sturdy stone above the moving lava and in contact with the water.
Add the cracked red nether brick and the sculpted red nether brick but this one would have a blaze head same for the blue nether brick except that the sculpted blue nether brick has an enderman head.
Redesign of the dungeons there are small, medium and large ones inside we systematically find mob heads with slime spawners that can generate themselves too.(Creeper ,skeleton,zombie,spider,slime)
Add the blackstone and deepslate pillars.
add variations of colored leaves (you know blossom trees) but with flowers
That spore blossoms can be used to craft magenta.
Add sturdy stone variants for blackstone and deepslate and perhaps other types of rock.
Azalea leaves with flowers can be used to craft purple dye.