With dashboards we can hide more than we show. :-)
This is a really good thing ans yes you have addressed very common problem.
I'm not sure whether I am understanding your requirement or not, but you could also just put the Quarters pill onto the columns tray twice in a row, and the labels and headings will then appear at the top and bottom of the graph.
Or is that not what you are wanting?
The issue is that I want the headers that are used for discrete date aggregations, but want to have an unbroken line across years, which is only possible with continuous date aggregations. Thanks for the suggestion though!