+100!
the customizer is vastly underused by 3rd party theme developers. i’ve finally been seeing some shifts from theme options to the customizer in the last few months, but the implementation is often rather messy, esp now with widget panels, etc.
i think the customizer vis-a-vis random theme options panels is vital to somehwat standardizing/optimizing the theme setup experience (esp for the DIY user). or maybe standardizing a theme options panel along with the customizer for live previews. either way, def needs discussion!!!