The first patch got thoroughly improved by review on the list, but hasn't yet been accepted into svn.
I've implemented similar functionality for vo_gl too, but it's quite hacky still. It is however possible to get bt.709 and studio level RGB out from it too. I'll attach a patch here in case anybody is interested. Use something like "-vo gl:yuv=2:colorspace=0:studio" for proper colors and studio levels.
Here's a sample of the difference using the right color space makes: