For ages I've had ~ remapped to escape (if no modifiers pressed so tilde still works as expected, and caps to ctrl) so the missing ESC isn't a big deal, although I did have it remapped for `

Anyone looking for extremely fine grain keymap control (with a UI that far surpasses any kind of keyboard remapping I've tried doing in Linux) should look up karabiner.

https://github.com/tekezo/Karabiner