Is there a script\fling that will migrate everything (clusters, hosts, DRS rules, storage clusters, permissions, folder structure for VMs, etc) from a 5.5 vCenter to a new 6.0 appliance?
There are several available that do the major part of such a migration.
See:
Cloning Datacenters between 2 vCenters with PowerCli, including permissions and many more
vCenter PowerCLI Migration Script
Cheap disaster recovery
And there is InventorySnapshot fling.
I propose you have a look at those (and others), and let us know what is missing for your specific environment.
Wow, that was everything on my list.
Thank You