Yes, this would be useful.

You can perform hit-testing for axes with the PlotModel.GetAxesFromPoint method at the moment, but it's not quite what you describe (would need a bit of fudging).

I already implemented this in the my fork. I currently have two different areas for the axes area and for the title area. Filling the two areas with two different colors looks pretty fine for all available examples.
Maybe you can have a look?

I'd be glad to if you can throw me a link: I don't see it in your fork, but I might just be missing something.

Forgot to push... My fault. Sorry

Works for all examples in the solution. Show case: filling the areas on rendering.

For the AngleAxisRenderer as well.

Some interesting stuff in there, couple of notes from a quick scan:

• Would prefer Annulus over Hypoid (I think hypoid is a more specific concept? feel free to correct me)
• Would be cool to see if we can use this idea to simplify the GetAxesFromPoint method (and so make it easier to add new axis types)
  • The hit test areas are different; having labels and title separate is useful: may want to add another region for the 'whole', possibly extending into the plot area, though this might be ill defined at the moment
• IShape might not be the best name, but I can't think of a better one right now
• Not sure about the TODO about adding a margin to capture clicks; that probably shouldn't be the axes' concern, or if it is, it should be a margin property that is configurable: can you expand on the idea there?

Feel free to open a PR for this: will make it easier for us to discuss specifics

Regarding your points:

• Rename Hypoid to Annulus -> valid point: done
• I renamed AxisArea to AxisLineArea (green) -> capturesjust the AxisLine, TitleArea (blue) stays the same and added another AxisArea (red) for the whole Axis
  
• IShape might be better IContour, but this would be a minor one
• the TODO is about the following: what if the major/minor tick length is zero or TickStyle is None and the there are no labels drawn due some use case specific reason. This would result that the AxisLineArea would be equal the line stroke dimensions. For user interaction maybe not the best, as it will be very hard to select it with the mouse (e.g. my application is mainly driven by mouse interaction to select an configure -> all elements are wrapped in separate viewmodels).
• will open a PR