In this paper, we present the initial evaluation results for extended GATE / REPORT MPCP DUs proposed as an extension to the IEEE 802.3 ah standard flow control mechanism. The obtained simulation results indicate the superiority of the proposed solution over the currently existing systems, in both bandwidth conservation and QoS support, as well as system design flexibility. Thanks to the extended GATE / REPORT MPCP DU per queue, centralized packet scheduling can be maintained at a bandwidth cost approximately equal to that of per ONU scheduling, with the added benefit of typically 100% system capacity upgrade, in terms of queue count per LLID, with no inherent increase in the number of LLIDs assigned per ONU (assuming 8 or less queues per LLID at deployment time). Bandwidth conservation, added flexibility, and complete backward compatibility, as well as coexistence of extended and legacy devices within the same network structure without any collisions, are just a few major features of the proposed solution.