It seems to me that modern airliners are optimised for the carriage of passengers and their luggage, sometimes even to the same airport. As such, given the constraints of aerodynamics they will all start to look the same. Also, as you have touched on, it must be acceptable to the passengers who will be the end consumers.
I personally think that airline execs are unimaginative people who wouldn't be interested in anything unusual before someone else has proven it is profitable.