You might be able to make one of the speaker grills and hide it under that... and put some hinges on it.
So you open the grill and there it is.
what I did for my defender cab (standup) was to put it right behind the coin door. And took the key off, added a handle to the coin slot... so now you open it up and there it is. I wanted to hack the dreamcast to have the top always off. And hook the dreamcast open connector to the coindoor (so when you opened the coin door, the dreamcast thought you opened the dreamcast.... Then mount the dreamcast to a board that entirely closed out the coin door....
but I got it working just sitting inside and go with that...
but having it right inside the coin door works pretty well for changing games.... but you have to remove the coin mechs.