Inherit RadDiagramConnector and add it to a Shapes' Connectors collection. Copy / Pasting (or other serialization / deserialization action) the shape creates RadDiagramConnector, not the custom type of connector.

ManipulationAdorner (including Rotation thumb, resizing thumbs) should not be zoomed along with the shape.

Currently the Bezier Connections Start,End Points and the two editing points are created in a common Canvas. There is no mechanism to hide the editing points but show the start and end point.
Note: Currently there's a way to hide editing or intermediate points - you'll need a style and a converter. We've added a new SDK example (HideBezierHandles) demonstrating this.

Users need to create custom mouse tools and set them as ActiveTool of the RadDiagram.

Users should be able to easily customize the Pan operation of the diagram.
Update: With Q1 2014 you'll be able to customize all the diagram tools

Extend the serialization process to save the type of the custom connectors along with their most common properties - such as their Background, BorderBrush and size.