All depends on how it works tbh, and which one your using, you could write your own script to set pos in the air and assign the halo jump command with "addaction" if player altitude (z co-ord) is above 1k, with a direction [180,[232,213,1000]]
[direction,[x co-ord, y co-ord, z co-ord]]
you would have to check the co-ords your player spawns at and do some if commands to say
if x co-ord is below 10k then get pos player, replace the direction to face north, but keep the xy the same, set the z to the height u want
then add into ur self actions the code for adding an action if the player z co-ord is above 1k, this means ur players cud base jump if the building is high enuff and the setting for z c-ord is high enuff
I would also build in a check that if player is below certain height to remove the addaction so halo jump is not always there
I personally however dont have the time to write it up, but there is a brief summary of what is needed if someone with the ability wants to write it up