I went over all 16 pages of this thread - some really solid wish lists for 5.1 but I'm gonna volunteer some weird ones;
KT Tunstall's catalog. I am a MASSIVE fan and I just think Eye to the Telescope or Tiger Suit would be great in 5.1, not sure who should mix em but. Telescope is the one that has a snowball's chance on a summer's day of happening, but if I had my pick it'd be WAX - gritty sounding but thickly layered and begging for surround.
My other one is Talk, the ultraclassic long forgotten 1994 album by Yes. Aside that it is excellent and Endless Dream screams to be 5.1, it's one of the first fully digital albums, it was made with like four Macintosh PCs ganged together and stored on a bunch of 12GB hard drives. Its production and mastering are beautiful and clean, fuuuuull of dynamic range. It's ideal for it, so just do it. Steven Wilson, will you put Talk into that theoretical second batch of Yes blurays?