We have been working on a requirement (AEM 6.4 - Touch UI) where when an asset is uploaded, we will have to determine the aspect ratio of it and if it's invalid then throw an alert which could prevent the author from uploading the image OR Display a Coral-UI alert message which shows up when the image is viewed(something like "Invalid aspect ratio"). So, basically asset validation and error message display. We could accomplish this particular requirement through overlays in our AEM 6.2 environment. But in 6.4, there is a new feature/restriction like Internal (granite:InternalArea) which prevents few nodes in the /libs from getting overlaid and inherited. We understand the reasons behind AEM coming up with something like this. Read here:: Adobe Experience Manager Help | Sustainable Upgrades.
Now, the nodes we wanted to overlay are greyed out and hence we could not proceed further with this customization. So, what are the other options available to perform validations on assets and respond with alert messaging accordingly. Pls. let me know if you guys have gone through similar stuff in your past experience. Thanks in advance.