So there is no other chance to make it easier than to enumerate the whole Keyboard and transfer the string "w" to Event::Key::W.
Your Idea would be to represent the whole keyboard with numbers, but that is still a lot of work, just think about the numblock, the F-Keys and the normal Controlkeys like Shift, Control, Alt, Left, Down, etc...
Anyways, thanks for your thoughts, i think i will use the numbers.