I'm assuming F122. Why? Because that's all I have for reference.
1. Room for a Teensy? God, yes. If that's all you wanted to put in, the amount of space is like a palace for that Teensy!
2. Room for the Raspberry Pi? Yes. to the right of the function keys and above the numpad (actually, it's above the home, end, etc "six pack" because of the shape of the metal plate and the built in feet), there is a space that looks like it would fit a Raspberry Pi comfortably. That doesn not take into consideration the cables, so you might have to solder them directly to the Pi instead of using the ports.
3. Room for both? You can fit the Teensy just about anywhere, so yeah.
3.5 And a USB hub? Likely it can fit beneath the metal, but not there the controller is.
4. The Commodore 64? The system that was a computer built inside a keyboard? (or the keyboard built into the system's case, depending on how you look at it):
Show Image
(http://upload.wikimedia.org/wikipedia/commons/c/c9/Commodore-64-Back.jpg)
thanks!