VMware ESXi – how to deploy a VM from OVA and prevent it from booting automatically

You can manually assign a MAC address (as you've stated) and you can manually specify the UUID by editing the .vmx file of the VM.

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1541

So, I probably should have rummaged through some of the other cloud providers... like there is this 'exoscale' provider which provides a bash script and a unit to fire off that bash script...

  - name: exoscale-cloudinit.service
    command: restart
    runtime: yes
    content: |
      [Unit]
      Description=Cloudinit from exoscale (cloudstack-style) metadata
      Requires=coreos-setup-environment.service
      After=coreos-setup-environment.service

      [Service]
      Type=oneshot
      EnvironmentFile=/etc/environment
      ExecStart=/usr/share/oem/bin/exoscale-coreos-cloudinit

...and the method of getting CoreOS to parse a cloud-config via URL...

#!/bin/bash

. /usr/share/oem/bin/exoscale-dhcp

DHCP_SERVER=$(get_dhcp_ip)
USERDATA_URL="http://${DHCP_SERVER}/latest/user-data"

block-until-url "${USERDATA_URL}"
coreos-cloudinit --from-url="${USERDATA_URL}"

...but now I have a bit of a chicken/egg problem unless I have some method of getting a temporary IP address to perform the curl operation...