I did my first control panel without one, but it was a conversion cab. I actually used a router attachment for my rotary (Dremel) tool to cut down the areas for the sticks. Not exactly time efficient, but it worked. Since I've moved on to more complex cabinets and panels, I consider the router pretty indispensable. If you intend to scratch build anything with t-molding on it, there really isn't any other tool that you can substitute.
I don't find the need for a lot of bits, because arcade cabinetry is very basic when you consider some of the routers more complex uses. I would suggest having a 1/16" slot cutter for t-molding, a flush trim/pattern bit (one with a top, one with a bottom bearing) if you plan to "trace" any cabinet sides or control panels onto new material, and a couple straight bits to cut your control inlays.
I also have a set of roundovers for copying Williams style control panel fronts, but thats about it.