Thanks @Danal and @T3P3Tony!
@Danal: that's good out-of-the-box thinking there, I guess my background as a software engineer shows: I prefer to do as much as possible in software. 🙂 I see how your circuit solves the issue, yet I worry that it's an extra component for me to manufacture and calibrate for every device I want to ship. Hence my eagerness to do this in easy-to-reproduce software instead. 🙂
@T3P3Tony cool, I had no idea the 3.0 firmware is in the works! I love how pin selection becomes so much more flexible and understandable. Yes, triggering on an analog threshold for M581 would exactly solve my issue, I'll post in the feature request sub forum!