Well, I would think that the CP could be made bigger, but you would want to layout your controls (print paper templates), and mock them up on cardboard, before you do any cutting.
As far as 4Player cabs, there are many examples here (look in Project Announcements, or search for 4P CP),
What I would recommend (I am building now) is a UA2 cabinet (although many here will groan because it is common, it is less common than Lusid's design)

The guy who runs this board, is called Saint, he actually sells a book called
Project Arcade, that it excellent (I bought it myself). The book is about $20 (check different vendors), and has step-by-step instructions for building Lusid's cab, but also has diagrams/instructions to build the UA2 (Ultimate Arcade 2) cab from mameroom.com. Although I don't think there are specific plans for a 4P control panel, there are many links, and you can purchase mameroom.com's 4P CP plans for cheap,.
If you haven't built a cab, buy the book. The info in there, is priceless.

Even a total moron who has never done wood working, computers, or electronics, can figure it all out...think of it as "Arcade Cabinet building for Dummies"...like me.... :
When you start your Cab, please start a new thread in Project Announcements, and keep us updated with LOTS of pics, and progress. It helps others, and gives the guru's something to laugh about.
"Look at how many buttons the noob has on his Control Panel"
"Oh, another UA2 cab, with crappy artwork, why cant the noobs make anything original"
"Those noobs never search, they just keep asking the same dumb questions over and over"
Just wear your "thick skin", and keep an open mind. Most of these folks are great, and very helpful, some not so much (you know who you are)

Good luck.