The only thing I can think of is using a Shape chart to mimic the Merimekko chart. You can cut the bars in any way you like and even show different colors for every bar that are stacked on top of each other. This might take some extra code in order to make it look like the chart since there is no Merimekko chart out of the box.
Developer in Technical Support
Xceed - Multi-talented components - http://xceed.com