It is possible to use the second side if your using a Jamma cabinet. I found a VS board to Jamma adapter that lets you switch games by button press combo.
http://cambridgearcade.dyndns.org/?q=node/38Combine this with Multi-Vs kit X2 that would give you I believe a maximum of 16 Vs games on a single board.
https://www.highscoresaves.com/nintendo-multivs-lite-multigame-kit.htmlDownside is none of the daughter card games are supported and you would really hack up your unisystem to get the jamma adaptor to work.