You're on the right track. In all honesty, as far as design goes, Panda and Warehouse have the vast majority of needs covered. Some of their stuff is getting out of date as far as demos go, but as you said, but if it can be easily adjusted with CSS or some basic HTML, it's not too big of an issue.
When it comes to design needs, I typically look to large online leaders in the same industry to determine an approach. As long as I can easily recreate a site that looks and functions similar to global product design leaders like Patagonia, Apple, Herman Miller, Nike, or a few others, then my needs are met. If you see their sites, you'll quickly notice some holes in availability from the above mentioned themes that you could easily close and make your theme very valuable.