I have a thought on this in regards to having diagonal keys.

xbindkeys allows for mapping multiple key presses.

The problem here though is that you can't map out something like
w & a
only
Shift + w or Ctrl + w

If you were to use Xmodmap and change the value of w to the Shift key, then you could map w & a to something like down and left.

The other thing would be to hack xbindkeys so it's not as restrictive with multiple key presses and would allow such things as mapping w & a.

Maybe there's one person here that I didn't confuse with this idea.