It could, but the goal would be to store the code as rich text not plain text. So it would have to be decomposed to an AST and then stored in some structured fo

It could, but the goal would be to store the code as rich text not plain text. So it would have to be decomposed to an AST and then stored in some structured format - XML for example. This means that all of these existing tools that deal with just plain text would need modifications to handle the richer file format. Having it as rich text in the editor and then saving it out as a plain text file means you're just making a rich code editor.