I use latches similar to the ones pictured, one on each side of the control panel (on the inside). I have to reach through the coin door to access one, and the front door to reach the other. Not a bit deal as long as you can reach inside far enough...
For connections, if your interfaces are USB and attached to each control panel, then you just need to use USB (have a mini hub on the panel if there are multiple interfaces). I do this for some panels, but for others, I have an IPAC inside the cabinet which I connect to panels via molex connectors. If I did it again I would probably have a cheap USB keyboard/gamepad encoder in each panel and just have one USB connection (per panel) to the cabinet.
Of course if you are powering a load of LEDs etc on your CP then you'll probably need a powered hub on your CP, as lamprey was saying.