'Rubber' lines.
 

Does anyone have already, or the ability to create lines (with or without arrowheads) that stretch visually to create the appearance of 'rubber' lines?

What I have in mind is, a situation in which one could specify a lines width as per usual, but have the option of additionally specifying a 'minimum' width or constriction point. This could be applied to the line like a special sort of node that could be moved along the line like a label currently is. I envisage it causing the width the line to be distributed along its length (i.e. from each end toward the node like a single bezier curve appliec to each side of the line), with the overall effect of having the line appear to 'stretch'. In the case of arrowheads applied to a line: the arrows themselves would remain as they currently are, with the line 'stretching' from where it joins them.

Sorry if that's a bit wordy. Hope someone gets the gist of what I am saying and can help. It would add a 'dynamic' dimension to the use of lines which doesn't seem to be available currently (at least not in the standard version).