'why the decision to start breeding? What sub-species will this be?'
This isn't a decision as such at this stage, just a long-term aim or strategy.
Generally, the zoo has taken the decision to concentrate on felids and prosimians, with some other small geographically complementary species, to form a sort of asia-madagascar themed zoo. The emphasis on tigers will remain; even if feline breeding resumes it's hoped that there will be room for some rescued or surplus animals*. It's envisaged that all primate intake will be under the auspices of the appropriate breeding authority.
*From a personal point of view I think it's wonderful to see how well rescued cats can come along when given the right care & environment.