Greetings.
I'm no coder nor I intend to intrude in any way with Zedwick awesome work regarding Zedwork.
There is a simple way to prevent anyone to even set a "foot" above The Nether ceiling.
I have used this code before on a vanilla server with total success.
This code as been tuned for 1.12.2 but the concept it comprises can be easily modified and for sure compacted and simplified by Zedwick for the 1.13 version.
Always active and repeating command block:
-> scoreboard players tag @a[m=0] add Nether {Dimension:-1}
Always active and Chain Command blocks:
-> execute @a[tag=Nether] ~ ~ ~ scoreboard players tag @s[y=128,r=1] add NetherCeiling
-> execute @p[tag=NetherCeiling] ~ ~ ~ tellraw @a ["",{"selector":"@s","color":"light_purple"},{"text":", you're not allowed in ","color":"green"},{"text":"The Nether","color":"red"},{"text":" ceiling.","color":"green"}]
-> execute @a[tag=NetherCeiling] ~ ~ ~ tp @s[y=128,r=1] 0 64 0
-> scoreboard players tag @a remove Nether
-> scoreboard players tag @a remove NetherCeiling
*Instead of command blocks, a function can be created.