I have had some second thoughts on the 4 way placement also, I like that it is in the center of the CP but can see issues with the trackball.
As for the switchable in my craze to get started I already ordered some buttons, the IPAC2 and the joysticks. I also want to keep this as simple as possible. I want it to be as easy for my kids to use 5 & 11, the 11 year old no problem. But I want the walk up and play. I have had too many projects in the past where in the end it has some tricks. My test is if my wife wants to play it (which I doubt she will, she just doesn't appreciate what a great waste of time) and I explain it to her she can play all these games but she has to remember to change this switch for blank or ..., I know I will get that look. Also I really like the look and feel of the ball top 4 way on pacman and galaga.
I will attach a side view of the CP to give you an idea of scale
the distance between center of track ball and post of 4 way is 7.125"
Do the six buttons have any use except for fighting games? (thanks Buddabing) I want it to be as flexible as possible also. I can just see some friends coming over and are real big fans of a game that needs them.
Also a lot of layout have the thumb button below the six, what is it's function?
I also like the classic look with the smooth sides but a removable CP just makes too much sense, and in the long run more comfort. I am not a stickler on making a super realistic cabinet, just a good balance.