I think it's an interesting idea, and one that most theme-developers would welcome with open arms. Anyone who has ever built more than 1-2 themes knows that at their core, all themes are the same. They all have the same components. It's just a matter of how you tie these components together and how you style them. Currently these components don't exist, we have to create them again and again and again - each time just copy-pasting code we've already written - and tweaking details when needed. Every time we build a theme there's a little voice in our head that says "I'll just call this div `.blog-layout-whatever-because-why-not`". A consistent unopinionated base that would set the foundation for everything else would be a lifesaver both for themes and plugins. Frameworks are good, but I always reach a point where I start stripping stuff out of them. They try to accommodate all cases and therefore by necessity include things that most people will never use. If on the other hand WP-Core had a consistent method for naming things, then everyone could just use those and there would be no conflicts between themes and plugins - provided of course they both respect their role (themes take care of appearance, plugins functionality).