Layouts, Switches, anything!
How about keys that contextually change their function and symbol? I'm hoping this becomes a normal thing in the next decade, it could make using a computer much more efficient. But for now, it's expensive, and software support is not very widespread.
I was stoked for these when they came out a few years ago. I could think of tons of uses for it- gaming, digital audio editing, etc. It's a shame it still hasn't really caught on
I was shocked how much more comfortable a ortholinear matrix layout is for typing. It looks like it's a big change and you need to adjust for a long time, but I got used to it within a day and even fixed some poor habits. And while we're talking about matrix layouts: the space bar doesn't every need to be that big and is such a huge waste of space, it makes me mad. I started using a grid layout and thought it might feel weird and I'd have to set multiple keys to space, but I only ever use the size of one letter key for space. Now I have about 5 more keys to use for other things (space bars are traditionally around 6 key units long). If you want to look at what I'm typing on, it's the Planck keyboard on ortholinearkeyboards. I bought it as a side project while waiting for another keyboard, but love it more than any other right now :)
I wish there was a cheap way to try it out, but consider that smaller factor keyboards allow for less travel of the hands. It's like touch typing has been upgraded to include arrow keys and F keys and of that jazz. Maybe try a 60% board? Also, the Ergodox has more keys and is ortholinear.
I don't mind the backspace and forward delete keys being hard to get to. Makes accidental deletion occur less frequently.