I think you might be missing something easy, or maybe it Is time for a new remote with a little more real estate.

What I did the other day on a Pro Control and (current) Denon setup is add two buttons. One button labeled "All Speakers" which does "Mode Multi-Chan Stereo". Another button labeled "Movie Sound" which does "Mode PL2 Cinema". Then I just copied those buttons to each source. A couple months ago I used the "Mode Scroll" for a button to scroll through each surround mode on a Marantz.

I understand it's slightly different, but I'm sure if you dig through a few more codesets, I bet you can make it work.