[JEEB]

The two things you bring up are separate, that's the first thing I'd like to point out.

• A fully 10bit YCbCr playback chain up until the RGB conversion. This is right now attainable through mplayer2/mpv with the gl3/opengl renderer, as well as MadVR. Both can take 10bit output from the decoder and then convert it to RGB (possibly with dither etc., MadVR is still limited to 8bit RGB output)
• 10bit RGB output from 10bit YCbCr. This is not really /that/ important, as 8bit BT.709 YCbCr is like 1/4 of 8bit RGB's colors to begin with even with full range content. So if there really are more colors encoded in the 10bit encode, it should be visible just fine on a proper 8bit RGB monitor/connection as well. This is why in general I try to separate these two things, and tell people that they do not need 10bit monitors to enjoy 10bit encodes of things. Yes, I know just comparing color amounts without taking into account a couple of other variables isn't fully correct, but you get my point methinks.
  
  But let's put that aside. You want 10bit YCbCr to be converted to 10bit RGB. To my knowledge, wm4's opengl-based renderer in mplayer2/mpv (gl3 in mplayer2, opengl/opengl-hq in mpv) should be able to do that just fine. MPC-HC's custom EVR-based renderer can also output 10bit RGB -- but it also cannot do 10bit YCbCr input yet.