I think all of the Return to Forever albums on Mercury before Romantic Warrior (Hymn of the Seventh Galaxy, Where Have I Know You Before and No Mystery) would really benefit from 5.1 remixes as well. The original stereo mixes of these albums are amongst the worst I've heard from the 70s, tinny with no bottom end.
In fact, in 2008 when the "classic" lineup reunited, Concord put out a 2CD set called The Anthology that compiled about 80% of the band's output from 1973-1976, and it was all newly remixed in stereo by engineer Mick Guzauski. Despite being a bit over-compressed (presumably in the mastering stage) the new stereo remixes reveal that these were actually superbly recorded albums, and that the old sonic defects in the old mixes were a fault of the mixes themselves and not the way the multitracks were recorded.
Given that Guzauski has some history with surround mixing (he worked on Chuck Mangione's two quad albums, and was Claptons 5.1 mixer of choice) I always wondered (hoped!) if he did the same thing as Bob Clearmountain did, making 5.1 mixes for his own benefit when he did stereo remix work. Guzauski also mixed Daft Punk's Random Access Memories in 2013, another album that I think would be stunning in surround.