Buttons above trackball will be awkward to click while using the trackball, and in games like golden tee or shuffleshot you will end up hitting them. The spinner may be in an uncomfortable location way up top, you might want to print a scale layout, place it on a board, and set it at the final height and angle you will have it, and then rest your hands where they will be when using each control, and see where your palms rest, where your fingers are most comfortable, and if you have to lean awkwardly to use the controls. I understand the idea of uniformity, but your graphics aren't perfectly uniform already, and your P3 and P4 controls are not mirrored, so why does it matter that the center of your CP is all lined up in some non-ergonomic fashion? Maybe shift the "mouse" buttons to the left or right depending on which hand you use to control the trackball, and look into alternate locations for the spinner if you find it is uncomfortable to use up there.
On mine I placed it toward the front to the left of the trackball, and it is comfortable to use and can be used with a wheel easily and comfortably, but it was in the way of trackball games like GT, so I recessed it and made an extension so I can just slip off the knob or wheel when not in use. I have a writeup of the process somewhere on this forum..
Other than those minor ergonomic points, it looks like it will work.