Adding a chart type: line chart with irregular intervalled x-axis.
For example, if you have 4 decadal data points for median income (e.g. [1980, $35,000]; [1990, $40,000]; [2000, $50,000]; [2010, $49,000]), and you want to show this data in a line along with annual data for 2011-2014 (e.g. [2011, $49,500]; [2012, $49,750]; [2013, $49,900]; [2014, $50,000]), if you use the current line chart option, each of these years will be evenly spaced on the x-axis but such spacing is not proportional the number of years between each point and I would like to see a line chart option it was.
This is what happens if I just simply add your data to a line chart today: http://jsfiddle.net/highcharts/etda3g4t/
Can you elaborate on what you expected? Maybe with a sketch to make it clearer.