The real restriction is whether the relevant authorities recognize the unit as safe/suitable, hence the existence of kludges such as invertors to provide 60Hz.
That's the issue at it's core isn't it. In order to install something as Basic equipment on the aircraft and satisfy our regulator to keep the aircraft on the AOC, we'd need to develop an STC and meet the certification standards for an appliance. To do otherwise would be to invalidate the Type Certificate.
Wouldn't the lawyers jump on that one when they sue because a bag fell out of an overhead and injured his client. Your honour - the aircraft was not even certified any longer and was not legal to fly yet they sold a ticket to my poor client ..........