Very interesting, for the 4 key, k and cntrl-d are really the only keys that would impact my vim usage much.

For heavy vim/emacs (I use evil/emacs) making sure your esc/meta/control keys are large and cleanly accessible is probably a better investment. I resisted even remapping capslock for years but now I'm even working on using control-[ instead of esc (it's universal but may not be the optimum trade for the esc).

Thanks though, I'll put this away for later.