In theory consolidating down to fewer regions is easier than breaking out larger regions into several smaller ones. You perhaps need to look at why a multi-region architecture was chosen in the first place - there are good architectural reasons to have multi-region, where a single region wouldn’t work as well.
You’d need to be aware of the geographic separation of the provider EMS’s and the location of your existing appliances. ManageIQ appliances assume LAN-speed connectivity back to their region VMDB database, so if your existing regions span continents you may need to consolidate your appliances back into a single datacenter.
Checkout the (admittedly slightly old) “Regions and Zones” chapter in the “Deploying CloudForms at Scale” reference architecture for some tips on regions and scaling: Chapter 3. Region and Zones Reference Architectures 2017 | Red Hat Customer Portal
Hope this helps,