Cascading selection

First : i love this module :)

The actual cascading selection behavior is :

on parent unselection, unselect children if all were selected

It means that if one of the childrens is unselected, when you unselect the parent, the selected childrens were still selected.
Example : ([X] = selected, [0] = unselected)

Step 1 :
[X] A
[X] - Aa
[0] -- Aa1 (children unselected)
[X] -- Aa2
[X] -Ab

Step 2 : we unselect Aa :
[X] A
[0] - Aa (just unselected)
[0] -- Aa1
[X] -- Aa2 (children still selected !)
[X] -Ab

Expected result :
I think the following result could be interresting : no selected children if parents are not all selected :
[X] A
[0] - Aa
[0] -- Aa1
[0] -- Aa2 (could be automaticly unselected)
[X] -Ab