Ideally it would be great to follow the lines of the barrel perfectly but it's a lot more challenging that it may first appear. The main problem is space, the curve of the barrel starts to taper quite a lot as it moves toward the ends and the wood itself is an inch thick, so you lose even more interior space for joystick bases, mounting and buttons etc.
An important part of the functional design was to have the controls as enclosed and protected as possible by the glass to protect them from drink spills which brings in the second factor you have to consider - the angle at which the players hands enter the small enclosed control panel area. It has to be shallow enough to be comfortable and allow the players hands to move freely under the glass without hitting the lip. This means you can't move the controls too far in as that increases that chance of contact with the glass by the top of the players hands, move the panel out too far then you have to extend the glass lip more, and then of course you are breaking the lines of the barrel even more.
The minimum width of the CP chassis is also heavily affected by the width of the monitor. I'm using a 17", you could use a smaller one but then you are sacrificing screen real estate and you still suffer from some of the other dimension restrictions anyway.
So could it be done better, no doubt yes. Could it be done as simply as it seems on the surface, absolutely not, the different factors involved all fight each other and it is very difficult to find the right balance of comfort, function and form.