I had gone down this road years back. (I have a Total Carnage machine). There are not many games that are twin stick shooters that I know of, so not sure if it's worth it. However, I DO have a separate MAME cabinet that has dual sticks for each player. What's great about that is there are a couple of good PC games that support dual stick co-op. Obviously I am running a PC inside so it makes it worth it. So I use that instead.
For my Total Carnage machine: My final solution was to get a JAMMA switcher in the machine. So now I can run the original PCBs: Total Carnage and Smash TV. In addition I can run a Williams JROK for Robotron, a ZooQ JROK for Space Dungeon and a Mylstar JROK for Krull (krull is vertical but JROK allows it to run on horizontal setup). YMMV, but it works for me!
Del