Return to Landing Page

Hi Everyone,

I'm currently working on a group of applications that represent different departments of the same company. We've  also implemented a Landing Page for unifying the access to a single link.

The challenge I'm facing is a request to be able to return to the Landing Page from each department site. Since for each department we're using different Site objects, it's not possible to have a 'Home' on the top ribbon that allows to return to Landing Page. We can return to the interface but the other pages/page groups remain visible and the request is to have them hidden. Obviously we can create a custom link or button somewhere in the site to allow the users to return to landing page but I haven't found any good front end ideas to do this in an organic manner. By the way, the users don't prefer the icon that shows the different sites on the top right, they even requested it's removal but I don't think that's possible. 

This is the header we're using for every page in the application: 

Have you guys dealt with a similar use case? 

Thanks in advance