I have created a bug report on Connect to have Data Deduplication added to Windows Server 2012 Essentials. Here is the link for it. I also realize that due to Microsoft's shortsightedness in handling the flow of information from the public of this public beta, some users cannot access that link at this point in time (even if they are on Connect). If you cannot access it, here is a copy of the description that I put in my Connect submission:
Data Deduplication - a role/service that is part of Windows Server 2012 Standard and up - is not available on Windows Server 2012 Essentials. It cannot be enabled at all (through the Dashboard, Server Manager, or PowerShell). While it may not be necessary to include setup for it in the Dashboard, I think it should at least be configurable in the underlying OS tools (Server Manager and PowerShell).
If you would like to see it enabled on WS2012E and can see the post on Connect, please vote it up over there. However, if you would like to see it enabled on WS2012E, have access to Connect, and still cannot see that link, please say so in this thread. I will post a link to this thread in my Connect submission so that any Microsoft employees that look at it will know if there are any Connect users that would like to see Data Deduplication on WS2012E, but were unable to vote for it because the submission isn't visible to everyone (at least at this time).
Thanks!