he is welcome to come back anytime

however, China has no place to host his officials.
Those nobilities and monks do not want to live as commoners. They want their old status, previlege and power back. There is no way.
Actually, it is not the Chinese central gov that does not want them back. It is the Tibetans. Dalai is fine as a symbol. But imagine that he comes back with all his offcials, they will take your position and let you pay for what you did in the past.