Multi-tier, multi-hop network architecture with integrated WiMAX-WiFi radio interfaces offers an alternative means of delivering broadband wireless access services to mass users rapidly and cost-effectively. Besides providing wireless backhaul in places where wired backhaul infrastructure is not ready or too expensive, such architecture can also take advantage of the complementary features offered by the two diverse technologies. Such architecture however inspires a wide range of complex and interdependent design considerations covering network topology formation, number of radios per node, ratio between WiMAX and WiFi radio/node, number of hops at WiFi multi-hop tier and so on. This paper attempts to provide some insights on how different possible hybrid topology designs perform in terms of required node (WiFi access point/WiMA Xbase station) density. In particular, we investigate how various designs scale towards two loading conditions namely the data rate per user and user density.