How to manipulate a data series like an Annotation?

I’m making an app for curve-fitting a line to raw data, and I’d like to have a way for the user to manipulate the curve-fitted line (shown in pink below) in order to fine tune their results.

Ideally, after clicking a toolbar button the line would have a callout box around it similar to Microsoft Word’s Shape art. The different markers on the box would allow the user to rotate the line or change the shape.

I’m wondering if you have recommendations for built in classes to use or extend? Currently the line I want the user to be able to manipulate is a FastLineRenderableSeries. I understand one can draw vertical and horizontal annotation lines and then manipulate those, but don’t think I can use annotations since I want to be able to manipulate the shape of a data series.

Should I be trying to extend FastLineRenderableSeries to make it behave like an annotation, or extend baseannotation to make it draw as a data series?

Thanks,
Jesma Secord