Hello Michael Gao,
I am sorry to see that no one replied to this question. I believe this is an ideal situation to consider a Tableau Online solution rather than several Tableau Server installations. However, if Tableau Online is not possible, please let us know by responding here. I will ask a few of our experts in house as well regarding this situation.
Later on we discussed ALPO architecture with customer, which is really reference-able. And I believe ALPO is a good example for global deployment in large organizations.