We think that the best way to implement this functionality is:
1) If you want the background to be zoomed in and out you could use a custom shape and set the image as its background. If you don't want your document to be scaled you could directly set the image as a diagram background:
2) Again use custom shapes (or ordinary RadDiagramShape with transparent background) and a custom dragging service so that you won't be able to drag a shape outside the document.
3) The zones should size correctly out of the box but unfortunately you can't keep the border thickness fixed because we're using scale transformation on zoom.
4) To restrict the panning will be a little bit harder because it's coupled with the zoom logic. With the latest release we introduced a way to customize the diagram's tools and this will allow you to customize the panning operation itself but to limit the pan when you zoom out you'll also have to handle the ViewportChanged event and BringIntoView the correct viewport manually.
I've attached a sample project showing those things so could you please examine it and if you have more questions feel free to ask.
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