Earlier quoted context omitted.
You can keep the normal layout on a 40%, you just wouldn't have number/function/nav keys without layers 40% is not just plank, and I personally find the ergonomics of a plank board to be rather bad compared to staggered, unless it's split.
That reminds me, I consider losing arrow keys a dealbreaker. I use them frequently enough to navigate both text and code in various contexts (except in Vim, which I don't use exclusively). I already hold modifiers to jump to next/prev word boundary, page, start/end of continuous data ranges in Excel, etc. Admittedly, I'd probably adapt, but I'm held back by the belief that any ergonomic advantages of moving to wasd o…
You can easily use your right pinky to hit Fn and then use the arrow keys that are right under your fingers (I think it's actually better than normal keyboard arrow key placement).
I don't think I could go below a 60% board because having the number row is too useful and dealing with function layers for that (and memorizing symbol placement) seems like an unnecessary pain for style.