In my opinion it is absolutely obvious:
1. The ability of the keyboard to generate all 105 ISO-scan codes as minimum. Including: F1-F12, Insert, Home, Page up, End, Page down, Print Scrn, Pause / Break, NumLock, Numpad keys. Please remember that if you personally do not use some button, this does not mean that it no longer uses.
2. The ability to reassign by Fn not only the F1-F12, but also other key: Fn+Esc, Fn+Caps lock, Fn+Tab, Fn+Delete, etc.
3. For the purposes of design, you can not write some additional action on the keys (enough to remember them).