you need to add a new structure y=256 x=16 z=16 filled with only air(use /fill ~ ~ ~ ~16 ~-256 ~16 air)
and in datapack you need to make to summon armor stands every chunk, like that
50
.
50.....0......50
.
50
0 = player position/one of chunks with the void
50 = chunks
and the armor stands will make a setblock for the structure blocks with the setup for void generating
if you ask how i know it i will say: "idk i just know how to do it but i dont know how to code it"