Beleive it or not most of the newer mahjong cabinets use a traditional keyboard.
That would makes things easier - if you find any pictures of a cab that kind please let me now/mail me!

Both me and my girlfriend like playing Mahjong much (haven't tried these arcade-versions, though, as they follow other rules and I guess I've to figure this out first), for my part of course I like the graphics of some of the games, too

A keyboard-like design would be not bad as this would be a panel that supports all you might ever need, so the idea isn't that bad. Maybe I should look after a industrial keyboard that I could build in a controlpanel - just have to see before how they make this in the real cabs.