+1 for WooCommerce integration points - we're using WC with about 10 custom fields added with Meta Box and the UI could be much smoother if it were integrated with the WC Product Data section.
We do have a few custom fields in the WC tabs using a method similar to what this blog post describes.
Perhaps a Meta Box approach could be an extension that behaves similarly to the Settings Page extension. User could define custom tabs (as we do now for Settings Pages) and then use an arg to define that tab/page as their meta box location.
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