As an engineer, I would like to thank you from the bottom of my heart for such an insightful write up on force curves and how springs work. I think this might help take some of the Myth and mystery of how a switch behaves and why "premium" brand springs may not alter the tactile feel of a switch. Extra bonus points for introducing free body diagrams
One thing that might help people would be to start with a linear switch and then add the added complexity of a tactile bump. That way, they would get a nice graphical representation of hooke's law before we need to tell them that real life is actually more complicated then that.
After reading this, I really wish aftermarket springs were sold either by rate or with a specified deflection at their "wieight".
Thank you again for a nice insightful writeup.