SEO url's with nesting pages

In my current project we have a problem regarding to the prefered URLS
and the routing which come with it.

For now I have one model Page that acts_as_tree, thus has a belongs_to
and has_many relations with itself. This is of course very nice
because then you can create a nice tree like this.

Page 1

- subpage 1.1

   >- subsubpage 1.1.1
   >- subsubpage 1.1.2

- subpage 1.2

Of course this is a very logic way of nesting pages. Now the problem
lies within the SEO url we want for these pages.

With permalink_fu it is no problem for creating urls like or
But the last one isn't what we want.. the last one should be or even for the
next level

I can't come up with a routing that makes this possible.. Is there a
way to achieve this? and is it still possible to keep the application

Thanks in advance,