Hi Sunny,
The upper part of the quick launch while in the project details view shows all available PDP pages for that project. You cannot add a link to the Project Site for that project into this top area of the quick launch.
Why exacty doesn't your customer think the ribbon is not user friendly? The button that takes you to the Project Site is sitting on the ribbon, regardless of which PDP you have selected... how could this not be user friendly?
I hope this helps,
Hans
My EPM blog:
Projectopolis