I have a client who wants to have a MainPage with three Tabs, each of these tabs has a NavigationPage as the first child to keep the navigation local to each tab. The tab bar in the bottom should always be visible. This kinda works nice on iOS but on WP I don't really figure that the WP design allows for this.
So what I want to discuss is
A) There is actually an error if you try to do this. If more than one child is a NavigationPage any back navigation will fail on WP.
This isn't really a good design for WP, help me convince my client 
Best regards
Johan Karlsson