This is a really cool idea. Bringing different people together to enhance each other is what draws me to Design Thinking. A coffee-shop is an amazing place for an OpenIdeo meetup. I'm inspired: I'm currently thinking of some dating-style apps that will help people find cool Design Thinkers to practice and innovate with.
I think this is a great idea, Benjamin! I think a really cool part of this could be the visuals: presenting the massive hub of innovation happening in a way that pulls more people in, and lets them contribute. Have you seen MindMaps? Here's an example: https://www.mindtools.com/media/Diagrams/mindmap.jpg. I think it's a cool way to cluster multi-pronged innovation in a way that helps people relate to it, empathize, and contribute effectively!