I was still early in the game with only 5 characters when I heard about this. I was going to finish the base game before I get this dlc. I just installed it and my save files which I spent 60 more hours on became outdated with an instability warning.. Because it's an expansion I thought it would be added to the end of the base game content.
If I knew about this, I would have bought this right away and restarted my progress. I didn't see any warnings about save file incompatibility on this page.
This is probably my favorite fetish game of all time, so I'm happy to replay the game from the start. Maybe it's better that I played it the way I did.. My next run will be much more interesting with the expansion, after all.
I'm absolutely dying to know what your next masterpiece is gonna be! I wish for Odyssey of Gianna to go on endlessly.