Thank you QA-Themes for your response. I made this plugin experimentally, but this is originally the feature that should be equipped with by core. It is important that we can choose base theme to maintain the compatibility with existing plugin and theme. Base theme for Bootstrap may be developed (real, I am developing it). However, because CSS framework (include Bootstrap) insert the element for designs in HTML, CSS framework may not be appropriate for base theme. It is desirable for data and design(view) to separate if possible. But... If various CSS frameworks are equipped in core, The making of our theme will accelerate surely.