There's a crossed wire here somewhere, or you're just wanting to do twice the wiring that's necessary.
Adding more contacts isn't an option for anything but having to do more work. It doesn't make anything easier or the board able to accept more buttons.
You're wanting a 'blank' board made up to fit inside the Wavebird shell. It only has so many buttons on it before you have to go adding them to the shell. Just like the DuXe up there. It has at most 14 buttons, now imagine I'm going to wire up some new controller in there that has 16 buttons. Putting extra contacts on the DuXe board doesn't do any good as I still have to add some buttons to the shell somewhere. If I do that and add in more contacts, then I have to wire the new buttons to the DuXe board, then off to whatever controller I'm stuffing in there. That's pure pointless when I could just go straight from the new buttons to the new controller, and if anyone really wants 3 Start buttons (they have other issues to sort out first) then they can wire them to the same set of ST1 and ST2 pads that are for the only Start button that's even needed.
Again, if I were making this board up to hold the components of the Wii U's board, then having the added contacts makes perfect sense as the function is on the board, but needs a button that the Wavebird doesn't have.
That DuXe CL up there has this issue, because there is no Guide button on the Duke shell. I worked around that by using an AND gate IC, so when Select(Back) and Start are pressed the Guide button is activated, but I also have pads for the Guide button, so one can be added instead if one wants it, that's an option. That kind of adding extra pads makes sense because the CL controller has that Guide button and the Duke shell doesn't, but adding them in there on a blank setup like the very first DuXe board there is just waste as it makes for twice the wiring, from new board, to blank board to new button when you could just go from the new board to the new button.
