Complete in NXG, based on the response of GregS (the original idea author):
"Yes, NXG does have most of this - I hadn't realised that you could define a GVI completely on the Diagram, and leave controls unplaced on the Panel, including setting the connector pane - that's actually really nice. The one aspect of this idea not covered in NXG is the ability to define more than one Panel per Diagram, where you might save different Debug or Probe views of the same VI. But that's a secondary part - I think the main concepts are indeed implemented, so I'd be pleased if this was closed off. Makes me look forward to using NXG a little more now"
From considering a number of other ideas (see below), I want to suggest that the Block Diagram is the only item initially created when defining a VI, and becomes the place where ALL VI functionality is defined. The BD is the place where dataflow is specified and the functionality of the VI is determined. So it makes sense that the con-pane should be linked to the BD rather than the FP -- it defines the data interface between calling VIs to this VI. Similarly the icon often provides a visual clue to the VI functionality, rather than its FP look. So both con-pane and icon are natural components of the BD window.
From the BD, it should then be possible to define one, or more, Front Panels which provide user interfaces to the data. These FPs may contain some or all of the variables in the con-pane (why ever show Error In/Out?), along with some or all of any other controls/indicators used in the block diagram. In fact, the Probe Window is already almost an additional FP - just allow several data indicators to be grouped on a single window, and you essentially have a Debug Panel. It would be great to be able to save the Probe window (or several of them) with a VI.
Yes, there will be problems, not least that I'm sure some existing code assumes that an FP (and only one) exists if a BD exists. And that every control/indicator must have a FP representation.
Here's a rough mockup (though the Probe points could be "virtual indicators" instead):