Q: "I was curious if there was a product that can allow 2 players to play on JAMMA carts as well as working on a MAME PC. Not at the same time of course, but to be able to switch in-between the two. I know that I can get JAMMA (style) games on MAME, but I like the nostalgic feel of having an actual cart( or multiple with 6-in-one expansion) in my machine."
A: You can use a switcher like this http://www.multigame.com/jamma.html
and a JPAC https://www.focusattack.com/ultimarc-j-pac-2015-pc-to-jamma-pushbutton-and-joystick-interface-pcb/