The "factory" multigame switcher is called the "perfect solution" kit. It switches not only the JAMMA inputs, but the trackball inputs as well. Unfortunately, when you can find them, they are expensive.
I was lucky to get one.
I don't see any reason why you couldn't use any other type of JAMMA switcher, but you will need to look in to how to switch the trackball input as well... or perhaps the TB can be hooked to all PCBs without issue (not sure).
As for upgrade options, the next logical upgrade is Golden Tee Complete. Unfortunately this requires a new PCB/HD. The HD is easily found online, but the PCB you're going to have to locate. There IS a way to upgrade, but from my understanding, when the guy who was doing said upgrade was contacted by IT legal department, he wisely chose to cease to offer said services.