This functionality is achieved by using template
Steps to do is as follows
give one vm to the vendor, ask him to make changes
once vendor finishes it, poweroff vm and convert it to template
If your VM is 2008 and later you dont have to do sysprep. for others just extract the sysprep tool to the following directory in vCSA or vcenter
VMware Knowledge Base
This applies to even 6.5 and 6.7 vcenter
you dont even have to remember even the VMS hostname and IP address if your VMs Names are in sequence and IP addresses are in Sequence you just can create custom specification for the VMs
Create a Customization Specification for Windows
Then just keep spinning the new VMs from template using custom specifications. you will be asked to provide custom specifications while deploying new vms.
keep old vms till you can verify the concept, after that just spin new vms as required
Thank you