Let me get this straight. You're trying to change the Upstream port on your unit but unable to do so because it is not available in the webui, is that right? If yes, then do this:up this thread.
hw_ctree.xml, look for X_HW_UpstreamWAN. Change the value inside the double quotes to the following:0 (Optical)
1 (LAN1)
2 (LAN2)
3 (LAN3)
4 (LAN4)
LAN4 as the Upstream port for example, then it should read X_HW_UpstreamWAN="4".