AA VIPOW (as many call it eVIP) is only good for AA metal only - not AA codeshare or OW partners.
Since you are asking "upgrading," I assume that you are going to purchase Y tickets. If so, you can purchase tickets with stopovers as you like.
My brother and I are looking at DFW-HKG-BKK(-HKT). We would like to take a stopover in HKG. I know that I can do most of this on AA metal, and so I am assuming that the best way would be to use VIPOWs.
AA metal doesn't go to HKG so you can't use eVIP.