I've been able to work out that Button 0 and Button 1 are actually Left and Right Mouse (may be the other way around)
These can be assigned at the Controls > Customize Controls screen by clicking the Attack Hand/Open hand options and double left/right clicking (as you need to left click to start the assigning process)
Then, by using space for legs and E for head, the main controls sort of work ok.
I'm Currently using:
1-4 Weapon Change (sword, hidden blade, etc)
Space Legs
E Head
Left Click Attack Hand
Right Click Open hand.
That way, I can loot/attack mostly with the mouse. Pressing and holding W (up), E (head) and Space (legs), and directing myself with the mouse, gets me up and over rooftops ok.
I've only gotten to an early part of the game, so I haven't had time to perfect my keys. I'll update this post when I do, and let you know what is the best key arrangement (in my opinion).
UPDATE: The above works well, with Q/F in use for locking, etc.
This should be valid for AC:B too.
There are of course some game specific pads, there are also universal gaming keypads, like Razer Nostromo or Logitech G13. On both of them movement (i.e. equivalent of WSAD) can actually be done with just the thumb. I'm not sure how useful is that, but it's definitively different than WSAD.
Best Answer
F9 is actually a configurable keybind...you just seem to have missed it. Observe:
To clear a keybinding, see this question.