Hello,
Its easy to integrate MetaBox core plugin in theme framework but extensions are only available as WP plugins. I have to modify them to integrate in my theme framework and its hard to update extensions in future.
It would be nice if you can improve to load extensions automatically from meta-box/extensions/ directory like Redux framework does. Please consider auto loading extension from a theme directory(specially from a meta-box/extensions/).
Doing so would not break future updates(manual) of extensions. Extensions autoloading and availability as separate WP plugin would make extensions easy to use for developers and non developers
Thank you