Yesterday I completed the ballerina automaton and it works! The figure is still poseable and she twirls when you turn the handle. The box lid slides in and out. Quite proud of this little piece though you do have to hum or whistle a little tune as you turn the handle in order to get the full 'musical box' experience.
I've left the box plain as this was a prototype but obviously it could be painted, decoupaged, stained etc. Am now on the lookout for more boxes to adapt.