I get your point, just sharing some thoughts and ideas, but you are definitely the one who is making this keyboard OH, no one will say the opposite I think.

If you plan on making two shallow dimples to help guiding the open/close movements, that's already one potential problem solved. I am also very confident in the strength of the magnets to hold the Jolla firmly. My main concern justifying the second sketch is perpendicular force applied on the Jolla when you hold the opened keyboard. This lever effect can happen very often (several times a day) with enough force to detach strong magnets, and in that case, it's the 400 € fragile Jolla that falls on the ground, not the plastic keyboard (admittedly lighter and more solid). Of course, I wouldn't be that concerned if the Jolla was in hands when the keyboard is opened.

But again, that's your baby. Just sharing my concern as a potential consumer of the final product. I will be happy to be proven wrong with any mechanism preventing such issues, no worries!

(I disagree with statement 5. And with a hook, if you mean the triangular rail, you just have to make a cutout starting from one side, not necessarily going all the way to the opposite sitde. But that is off-topic, just replying.)