If you jump down a hole all the way past bedrock and into the void, your player teleports to the next dimension but will keep that momentum going into the next dimension. If the cloud platform is used, it will kill the player when they appear on the cloud platform.

In my modpack I've replaced bedrock with a block that can be broken. Dimensional stacking is the only way to reach each of the 9 dimensions, so players often dig a hole straight down from 64y to bedrock to travel between dimensions, and just jump down.

I've tried to add fall resistance below y1 but it affects performance to check their y level as often as I need to in order to prevent them from dying and to make sure they're teleported before they hit the bottom of the void.

Could you cancel their momentum when they get teleported to a new dimension through dimensional stacking?

I added this mod to my newly released modpack:
https://www.curseforge.com/minecraft/modpacks/jetpack-cat