I quite like Acorn's idea, these connectors or connectible lines could have an artistic value as well if you could apply a brush to them. Especially if as someone mentioned they could connect to each other as well.

I'm thinking for example a tree branch where you could edit the main branch and all the sub branches connected to it would move with it. Perhaps by having nodes at each end that would connect to other nodes whether on a shape or lines or even other connector lines like Acorn's idea but it would give you the ability to place a node where ever you want the connector line to join. But the connector would still need to be an editable bezier curve. Add in the ability to convert a regular line to a connector line might also be a useful feature.

If the moveable lines could be animated as well as flow charts and adjustable illustrations you could also create a rigged character. I know Xara's animation features have been largely ignored but now you might have a feature that would interest a wider group of users and be something that Xara might actually look into.