Suggestions

AsyncWorldEdit Plugin

Vintage80

(This is not the same plugin as FAWE)
AsyncWorldEdit is the alternate plugin for FAWE. It has features such as enabling physics (Which is not available for FAWE.)
Link: https://www.spigotmc.org/resources/asyncworldedit.327/

Vintage80

I can already smell the replies "Just use skript."

Viavir

In fawes config file set allow-tick-placed and allow-tick-existing to true and then when punching a sand or gravel block it will fall. And if that doesn't work use //fall