pavers on vegetative roof systems

It's not reasonable from a maintenance standpoint to have literally a 100% green roof; it's not good for the plants to be walking on them. The exemplary performance requirement says "vegetated roof system" -- I would consider a vegetated roof system to also potentially include a limited amount of non-vegetated material. The system you describe would provide most of the stormwater benefits of a vegetated roof. If your pavers meet the SRI requirements, that would also provide most of the heat island benefits. I haven't pursued this exemplary performance point myself, so others may have better insight.