Aside from modern political considerations, I think the more important question is what, in purely game terms does a Tibetan Civilization and/or Leader bring to the game?
I am by no means an expert in Tibetan history and culture, but from what I have read the Civ would have attributes based on:
Mountain terrain
Religion
Expansionist only in certain early periods.
Some interesting early multi-armed heavy cavalry (I remember seeing an illustration showing an armored horseman with bow, lance, sword, lasso, javelins, with the comment that the warrior probably wore a belt, suspenders, and carried extra rope to be completely prepared for everything!)
Adaptation to high altitude, extreme weather and terrain for the economy - heavy emphasis on herding adaptive beats like Yaks and high-altitude sheep/goats rather than cattle as well as adapted agriculture.
So, how does the game differentiate Tibet from, say, Inca?
I suggest that Religion is the key to Tibet's exclusiveness, but that makes Tibet in Civ VII an Exploration Age Civ.
So then, what are its predecessor and successor Civs?
IF it succeeds to a Modern Age China. I could see where that might miff the Chinese, but Civ VII proposes to do worse and already seems to provide a straight Chinese 3-Age progression, so I don't think that is a major break-point.
The only in-game predecessors at the moment seem to be either Han China or Maurya India, and again, the game has already proposed worse progressions, so they are doable. I suggest Maurya as the better choice because it speaks to the spread of Buddhism into Tibet, which ended up largely defining the Civ ever since. Quite possibly Tibet also unlocks if you have X tiles of Mountains in your Civ borders at the end of the Antiquity Age - just to keep it interesting.
So, the final question: what kind of Civ Design can we come up with for an Exploration Age Tibet that provides a distinctive set of attributes and potential playing opportunities in that Age compared to what has already been shown fr that Age?
Start your creative engines . . .