Earlier quoted context omitted.
The DOM is more than the proposed content map, because it also creates structure. I think the proposed idea is to basically create a structure without any content, then apply the content into that structure. The current split is CSS is presentation while HTML is content + structure. Unless I'm misunderstanding, this proposal would separate content and structure. I'm not sure where presentation would go; you could cer…
I'd be curious if there are any existing example implementations that you think demonstrate this - I'm having a hard time wrapping my head around how flattening the structure would make things better. A tree node structure for mapping content seems like it'd be the most efficient in all the ways I can imagine it.
How the panes are laid out could be accomplished through any number of methods. Absolute, flow, flex, grid, constraint solving... Or even parent panes using different methods for their sub-panes!
The point isn't to flatten the layout. The layout can be as complex as desired. The point is to remove content from the layout; a named mapping is just an easy way to associate content to layout panes for injection.