Exposure selected area persistence

Is your feature request related to a problem? Please describe.
When working on large series of pictures with necessary back and forth with clients, it is usual to go back to a picture and rework it multiple times.
It is then really efficient to find all the module settings exactly as we left then.
This persistence is working most of the time, but the selected area for automatic exposure is one setting that is lost as soon as we switch to another picture.
The actual behavior is that the default selected area, when we activate the dropper, is the one from the previously opened picture, which is not the problem here.
If I go back and forth between multiple pictures, I would like to restore the areas that I've defined them for each picture/module.

Describe the solution you'd like
No change in the user interface. Make selected area persist (saved in XMP file) on each exposure module.

Alternatives
I tried using the masks, but they are designed to limit the exposure effect, not limit the estimation calculation and apply to the whole picture.

Additional context
For the context, here is my usual workflow:

• I import thousands of shots
• I do basic grading to a large subset of pictures
• I send a first export of those pictures
• the clients feeds me back with selection
• I do more precised grading of the smaller subset
• Another round of back and forth with the client / settings adjustments

I usually apply a 50% lightness exposure to the face of the models I shoot as a quick setting.
I often add multiple exposure modules to rework the lights, but always go back to the "head" exposure module to reapply the 50% lightness.
Losing the selected area arounf the face makes me lose a lot of time as I work of dozens of pictures at the same time.

No files or tests are named. Start by tracing how exposure modules store their selected area and how per-image module settings are serialized to XMP; confirm the behavior across multiple exposure modules and images. Done means each exposure module restores its own selected area when revisiting an image, without a UI change.