I'm not expecting this to actually happen... but I would instantly buy a Mac laptop that let me physically separate the screen and the keyboard while continuing to use them both. Then I could set the screen up on a portable stand at approximately the right height and distance while the keyboard lived closer to me and lower down, perhaps even in my lap.

Right now the best I can do is to carry an external keyboard. But it's a pain to have to tote around redundant hardware. Of course, it's also a pain to be in pain after spending too much time using an un-ergonomic laptop.