Mysonos.com sonos streaming service would be a real solution. I would be happy to pay $5 dollars a month.
I think all of us that hit that stupid limit would like a real solution.
A server that handles streaming from all different sources that sonos accepts. 100k tracks on google music, 200k locally stored, 50k on deezer, 40k on soundcloud.
You want a million songs on random, no problem play random all. Your playlists change on those services, it updates your play lists. You want no repeats, then it won't repeat a single song until everything has been played. Next time you are playing playlist that playlist it still remembers what has been played.
You want multiple large (over the 10k saved in sonos) playlists, you can save them there.
I hit that 65k limit at 32k tracks on google music.