I don't think that would be possible to implement such automatic upload. But we consider if possible to takes photos during polygon recording. We had also an idea of photo point - little bit similar as you suggest.
Anyway I'd like to also mention that you can create simple points (attach photos to point) during polygon recording. It require to have polygon layer for polygon recording and point layer for photo-points.
I'd like to mention that this feature is partially implemented. You can take photo during recording of polygon or line. The photos are created as attachment for the polygon/line not for particular vertex.
we would LOVE to use Locus GIS for mapping of forestry projects in Malawi but we need to be able to take photos wherever and whenever - so I formally request a big "photo" button which captures a photo and waits until GPS Accuracy of X meters and after taking photo uploads photos fully automatically to our project backend as soon as wifi or mobile data is available (would be great to select each option)
I really like the way how SW Maps displays photos when captured during polygon-recording - maybe that can be used as an inspiration?