So, the issue with numerating the navigation menus is two fold:

1. What if a page has a top and bottom menu (so they would be nav-1 and nav-2), but then another page, in addtion to those, also has a new middle nav; this middle nav would not get nav-2 and the bottom would become nav-3…
2. The individual menus are actually not aware of each other, so it would be hard to innumerate them, without reverting to something like session variables or wp_options that would have to be consulted & updated on each nav build…

It could be that simply removing the ID would be the way to go… Still thinking…

Atg