Pie Chart with Lines connecting labels

[mrfr0g]

I'm trying to find out the best way of emulating our existing charting functionality with Ext charts. Basically I would like the labels in the legend to float outside of the pie chart, and have lines which attach the labels to the pie slices. (see image). The last time I looked at this in version 4.0.5, it seemed really difficult to modify and extend the internal workings of the charting system. Basically my questions are, What is the best way to start this project? Has this been done before?

Existing Functionality Image:
39407

[mitchellsimoens]

Basically all you need to do is add new sprites per label so when the chart is redrawn then you can add the sprites