The various chart types plot on different layers.
Line/xy-scatter in front of bar/column in front of area in front of
pie/radar/donut. The items on the secondary axis are plotted in front of
primary axis but only within types.
The only way I can think of bring area in front of columns is to make
the chart completely out of series plotted as area.
This example demonstrates how to plot variable width columns using an
area charts. Maybe you can use this technique to create the columns and
the area. http://www.andypope.info/charts/colwidth2.htm