It is quite common to want to turn an attribute of an entity into it’s own entity: E.g Sun elevation for automations. Temperature from the weather entity. Etc etc. This makes automations easier and also gives other advantages such as state history.
I think this is a great idea and will build it.
Probably plenty of templates which are no longer needed then for a lot of people as still there is a lot of data in attributes still.
Awesome, link to the PR when you make it. And would be happy to contribute.
We might even be able to use regex to detect YAML entries in the style of "{{ state_attr('x', 'y') }}" and {{states.x.attributes.y}} and suggest migration using the new repairs UI.
As this was not approved to have within core I have released it finally as a custom component if someone finds it here and is interested.
At time of writing not yet available in HACS default.