mixed environment of 6.0 and 6.7 hosts

Hi all,

I am looking to upgrade our windows based 6.0 esxi environment to a new 6.7 appliance environment.  I know there is an upgrade which is often problematic.

My question is, can I just add the 6.7 appliances into the current environment and perform a phased implementation/migration of the old hosts to the new appliance?

I have heard that when you install the appliance and point it at the current SQL environment it upgrades the Schema and therefore the older 6.0 Windows esxi hosts cannot communicate effectively.  Has anyone had this issue after a failed upgrade?

We have a SQL 2014 backend environment.

Thanks in advance for sharing your experiences