Can you make category mapping cascade?

Right now category mapping only works if you apply a google category for each child category. For example:

Category Sports/balls/football -> Google category xyz

then all the products in the football category will have the google category xyz.

It would be a big time saver if you could make the product feed use the parent, or grand parent product category if the child category is not assigned, in essence cascading the product category down.

For example if I have

Category Sports/balls/ -> Google category balls

and none of the child categories of this parent category have any assigned category mappings

Then:
Category Sports/balls/football -> Google category balls (the category of the parent or grand parent etc..)
Category Sports/balls/baseball -> Google category balls (the category of the parent or grand parent etc..)
Category Sports/balls/basketball -> Google category balls (the category of the parent or grand parent etc..)

Thanks,
Chris