The "template" use case was a very common one from iframes/framesets in the early 2000s, and the markup often looked a lot like your desired example.
My memory's hazy, but I remember it becoming more and more complex to maintain as the web's security and performance model evolved, as you needed to manage and secure all of these disparate, discrete DOM trees in the same page context.
Wouldn't what you suggested just been "reinventing" frames/framesets if you added the ability to arbitrarily pull in templates via the network?
My memory's hazy, but I remember it becoming more and more complex to maintain as the web's security and performance model evolved, as you needed to manage and secure all of these disparate, discrete DOM trees in the same page context.
Wouldn't what you suggested just been "reinventing" frames/framesets if you added the ability to arbitrarily pull in templates via the network?