International ROMs have the option. I'm running Echoe ROM and have the video call button to the left of the standard call button on the dialer and also on contact pages.
If I try to place a video call, it brings up the video calling screen with options to switch camera or hide me, and says dialing, but then fails and asks if I'd like to try a voice call instead. I'm not sure if it fails because T-Mobile doesn't allow it, or if it's because the other party doesn't have native video calling (I don't think I know anyone who does).
OP, if you'd like to PM me, I can give you my number to see if it works between two parties with native video calling. At least that way we could determine whether or not it's a network limitation.
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