Nice job that’s an interesting new node 
I had tried disabling collision for individual chunks a long ago without success, I will be definitely looking at the source!
–slightly off topic–
Speaking of destructibles, since 4.7 I’m having a crash when I try to apply force to the chunks per tick… but if apply force to an individual chunk only it doesn’t crash.
Do you have any ideas why might be happening by any ? 
I’m trying to do something like your rock vortex using forces.