I too am interested in the setup graphically depicted above. I see you say you're running vpn connections to your network where the remote sites have the same subnet as each other. This seems like it work for traffic originating from their side to yours, however, how does it work for traffic originating from your side attempting to travel to a specific network on the other side? Are you able to ping devices on both networks? And if so, what happens if their are two devices with the same ip address?
Also, along with the same question that was originally asked, has anyone else attempted this or been successful through additional static routes etc?