Don't update the layouts in Atlas_Core as you will loose your changes when you update the module from the Marketplace.
Create a separate module to serve as your company theme module and place copies of the Atlas layouts there. With menu option App / Tools / Batch update layouts you can set all pages now using Atlas_Default to use your layout instead. This works on Marketplace modules too, only you will have to do that again after updating them.
Usually, that company theme module is also a UI resource module so you can place your theme files in there as well. Put it in your private Marketplace and it is available in all apps you create for the company.
Then create a snippet, place your Dataview in there, it must use a datasource microflow or nanoflow depending on your needs as there is no context object in the layout header.
Place the snippet in your own layout.