How would one go about customising the on screen keyboard on a Microsoft Surface Pro? I've noticed that it doesn't have an alt or Esc key and I can't think of any good reason why those keys, among others, should not be there. In particular I want to use keys such as [ and ]. Also there are no up and down arrow keys.

I already have a type cover but sometimes I'd like to use those keys without having the type cover attached.

Ideally I'd like a way to enable those missing keys and perhaps to remove the ones that I don't want, such as the emoticon key.