Hi, thank you for your answer. All sounds very promising.
As the material I work with is basically visual (not text) (and my camera not being the best) I think the question can't be resolved, even with very large image files. One example (see screenshots attached): from this engraving I took a view of the whole engraving and one of the detail of the picture which is important for my work: the group of sculptures on top of the arc. So I would want to highlight this group in the item view. As for now I can highlight the section within the image, but only zoom in in the selection view (for which the image quality isn't sufficient, as you see), or otherwise switch to the second image, the detail view, but which is not referenced in the overall view of the engraving. Linking the different views through the selection tool could be helpful, especially if you have a lot of photos grouped in one item, and/or a lot of details in one picture. The latter is the case for art historical analysis, where the fonction of visually locating detail views in the total view of a painting / architectural ensemble etc., and being able to easily switch between them, could be interesting.
The second case I am thinking of would be - still in image analysis, but I think it could be useful for written sources as well - establishing connections or links between different images. Let's say you want to compare different treatments of the same motif (in my case, allegorical figures) in two different pictures, you could then switch between the detail views of the two directly, or also use the selection tool as a reference tool to other images (like a note that you post on the image, "see also...", except that the image shows up directly).
The other use you are mentioning I didn't think of, but this is fantastic! "if we render the image into the selection layer that would also enable us to overlay/compare two versions of the same image" This would be especially useful for formal/technical analysis in art history, but there are other possible scenarios where it could be interesting. So I am very much in favor of this. Also, adding specific metadata to selection views, as you mention, seems very useful.