•Launchers:
Launchers is a mod that adds projectile launchers, the projectile list is below.
Arrow, 
Egg, 
Eye of Ender, 
Snowball, 
Fireball, 
Ender Pearl, 
XP Bottle, 
TNT 
•Way to Get Launchers:
The only way to get the Launchers is to kill Wither Skeletons.
The chance of dropping a launcher is the same as getting a wither skull.
Good luck with your wither skeleton farm :)
And yes, you can use this addon in your "addonpack" :)