Hi Tom - Welcome to the forum!
FusionHub on FW 8 supports VRF How to Create Virtual Routing & Forwarding (VRF) for Multiple Customer Groups in a FusionHub
So either that or dedicated fusionhub per customer. Would need to know more about the core infrastructure / hypervisor options and levels of throughput / number of customers / remote sites to begin to advise which approach would be most ‘suitable’.
What country are you / your customer based in?