New feature request posted here:
It sounds like you're looking to reference all children and children's children all in one formula.
As you may know, the best way to do this currently is to add SUM(CHILDREN()) or COUNT(CHILDREN()) in each parent row and then SUM or COUNT the CHILDREN in the parent-most row (Ancestor 0).
I typically try to lock these sorts of parent rows to prevent people from editing them. That way I can chase down any admins that may have inadvertently broken my sheet.
Yes, Shaine, I am.
The use case where I ran into it was JOIN(COLLECT()), which quickly clutters up the Sheet with useless cells. At least for COUNT or SUM, each level has meaning and usefulness.