That's a shame. Not surprising though, I'm sure if it was possible there would already be solutions out there. Thanks for the info!
I did some digging and came across
https://github.com/tylpk1216/KoboPageTurner, I've merely skimmed it but looks like someone was able to turn pages on their Clara HD using HTTP requests and mimicking screen taps. They then made a remote & phone app to make these requests, pretty cool. I'll probably investigate if this could work on the Sage.