Feature Request: Add a site wide media pool for PageMediaSelect

A feature which i am really missing is the ability to select media from a site wide media pool. It is really quite a problem if i have lots of pages with for example customer logos on them and a customer changes its logo. At the moment i would have to update every single page and replace the logo. Or replace the logo in every page folder via ftp or ssh. Either way is not very pleasing and would be a lot easier with a site wide media pool.

I know that you can upload files into the pages/images folder and link to them in markdown directly, but unfortunately they don't show up in the pagemediaselect boxes.