David,
I just want to be sure I understand your situation. You need 40 VMs per site connected via FC and each site has a 3040 correct? I'm sure what you meant by the initial VMs, You are asking if you should fill up the first LUN before adding the second?
If that is the case, it doesn't really matter. Since Dedupe runs regularly it will dedupe as you add VMs so you will use the same amount of space if there is 3 VMs in the LUN as if you had 20 VMs in the LUN.
Some things you could consider to maximize your dedupe would include increasing the number of VMs per LUN. The official VMware best practice is 20-25 VMs per LUN but I just had a conf call with them and one of my VDI clients and we asked exactly how many we could safely place in a LUN. The answer was the classic IT "it depends". 20-25 is typical but if you have low utilization VMs or if you don't tend to use VMware snapshots, you can place more VMs in a LUN. 30-40 was a viable for my client. This will increase your dedupe ratio.
Another option is you could place more than one LUN per volume. Dedupe happens at the volume level so this can increase your dedupe as well. Doing this though can effect your restore capabilities if you plan to snapshot the VMs in the volume so you have to think that though first.
Your title says Automated Deployment, are you perhaps wondering if there is a tool to deploy the VMs remotely to each site?
Keith