The middle switches are actually DWDM management cards with very limited capability, to change the VLAN tag would ve very traumatic (have to reboot 200+ cards over the system). I am trying to avoid this.
Today I have routers doing this, I would like to exchange them to extreme switches which already work as components for other networks. Sure, I could use two switches, but then I would be exchanging 1 old router to two new extreme switches, not very smart design.