Abyssal Slander.

First, the Celestial Supreme will have to be a landed god. Two, the inhabitants of the plane must be weak, so the child of the plane will be vulnerable.

If the inhabitants of a plane are strong, then the Will of the plane might not awaken in the first place or might not appoint a child of the plane because it doesn't need to. 

All of these make the Gattling plane a rare and unique situation. Trying to orchestrate it is unlikely to succeed. 

A lot of things can go wrong with that plan. They could fail in their attempts to get the Will of the plane, but they will surely make enemies of the whole plane during the attempt. Origin gods and world gods will not watch on as they invade a plane and massacre its inhabitants in order to draw out the will of the plane and weaken it.