Sharepoint 2013 - Use a central list in a site collection to write/change from all subsites.

I have this site structure:

Root
      ---- Customer 1
                          ----- Order 1
                          ----- Order 2
       ----- Customer 2
                         ------ Order 1
And so on....

I need to keep track of some figures. So a need a "List" (or something) on Root level. I must be able to add and change items on Root level, on Customer level and on Order level.  

I thought about creating a list on each subsite and when I change or add an item that this would be copied to the list on root level. However copy items over sites is not that easy. This used to work in 2007/2010 but I dis not find a 2013/online equivalent:http://spdactivities.codeplex.com/

Maybe some solution would be to save an Excel file on root level and connect all subsites to that file using BCM? Is this do able?

Although I think I get another problem that way because each Order site needs to have some defaults when writing to the list.

Any suggestions?

Thanks, Mike