From what I found, if you have licenses, you can activate them then hack your registry to get the older clients to work. I haven't been able to reproduce that in my lab.
The size comes to the fact that I have metal brackets on the back of the monitors that fit the Wyse P20. If I can find something that fits that, I can just swap them out and it makes for a quicker set up and tear down of the room.
I came across this thread, and it the Remix Mini might work. http://mangolassi.it/topic/7992/remix-mini-as-a-thin-client/3
I tested connecting to the 2012 R2 server from a tablet and that works.