It's a shame nobody has posted another answer in almost a year. I've had the same concern recently as I'm wanting to test the VDI-in-a-box solution from Citrix without having to buy a lot of Microsoft products just to get going. There are several solutions available now that run on the server itself without the need of remote tools such as RSAT which, as you pointed out, are Windows only.
The first place to start is here:
This is where to find a free set of GUI tools that run on the 2012 Hyper-V free server core. Really amazing product.
Another option is the free tools from 5nine.com although they really would prefer you buy their fee-based product.
Lastly, many have reported good results with vtutilities which also run on the server.
Hope that helps. I had to do a few hours of research to find all of that but it is working well for me so far. I'm using an older Dell PowerEdge SC1430 with dual quad cores and 8 gigs of RAM. Very decent (for a test server.)