I will agree that this idea is a legitimate subject of a patent.
Potentially, it could be beneficial. Instead of having to remove one's hands from the keyboard to use the mouse, one just hits the "Mouse" key, and moves one's right hand up, down, or from side to side, right where it is.
"Chiclet" keys, to put a flat surface under the hands, would almost be de rigeur with this kind of setup, though.
Much easier, though, would be to put a nice big trackball below the right-hand Alt key, instead of below the middle of the space bar. Of course, that would mean also having to make a separate left-handed version of the keyboard. The idea being to facilitate, with minimum hand movement, operating a trackball with the palm of the hand, not the thumb.
A simpler way to do that would be to have a trackball with a low profile - where "above" (towards the screen) and "below" the ball, there is little extra space, and the two mouse buttons are directly to the left of the trackball, for the thumb to push. Left-handed operation would involve reversing the directions of trackball motion, not the meaning of the two mouse buttons.
Splitting the keyboard in half, and then putting a trackball between the G and H keys, instead of just having one of those little piezoelectric things, also comes to mind.