IS IT SAFE AND OK:      If you use the additional network ports (not used for the VxRail deployment) you are fine.      If you "borrow" port from the VxRail deployed vDS, you are exposed to single point of failure (no HA) and VxRail is technicaly "broken" until you return the port back.
We have a new VXRail system set up and operational.    We need to migrate our existing VMs from an old ESXI 5.5 cluster.    I took a host and put some VMs on it and attached it to the new VXrail Vcenter.    When attempting a cold migration with VM powered down, it works.    When attempting a live migration with VM powered on it does not.  It tells me that I can not change the network and host for a VM as the source host does not support it.    So, I've found a possible solution which is to create a standard vswitch on one of the VXrail hosts, give it the same name and attach same vlans to it as the old esxi host has... Make sure the port groups are named the same etc, and then it would work.    I hope this works, but my question is... IS IT SAFE AND OK to make a temporary standard vSwitch on a vxrail host and use it to move VMs to, and then move the VMs to the distributed switch and eventually delete the standard vSwitch that I created?  I just need to find if creating a standard vSwitch on a host throws eveything in VXrail system off or causes a huge issue. 
Is this safe to do?