I know things would be much easier if we just reconfigured our new VxRail to use the same subnet/VLAN as our existing VMware & SAN is using, so that I could just disconnect my hosts and reconnected to the new vCenter and then vMotion & vStorage Motion my VM's and data to that system, but I'm not yet sure if this is an option for me.
If you're going from ESXi hosts with FCP-attached storage to VxRail (vSAN), then you could just disjoin the hosts from the current vCenter and join them to the VxRail vCenter, then perform a migration of the VMs. As long as the ESXi hosts have management network layer 3 connectivity the migration of the VMs will succeed. There's nothing from a storage perspective you should have to change with either environment.
When I've done customer migrations to VxRail, this is how I've generally done it. I only pointed out that blog so as to remind you that once you swing hosts or migrate VMs (doesn't matter), them being under a different vCenter for management will have implications when it comes to your existing backup, monitoring, and any other processes you have in place that require communication with vCenter and depend on the vCenter-provided IDs being consistent.