I like the idea and would be happy to help with content and ideas about layout/design.
So my 1st pass thoughts:
1. Might worth to think about making web-site colour schema lighter. I think "dark mode" is good for visual observers, say if they read forum and do visual observation at the same time. The INDI with its remote/non visual nature seems to be different situation.
2. I can definitely prepare write up (probably in Research section) about INDIHUB.space network and how to use it/contribute your images to it.
3. Responsive design - this seems to be just a choice of UI/CSS framework with responsive design built in. Integrating forum might be tricky but I think doable. I think forum is its own thing and doesn't necessary have to look exactly like Web-site.
4. When I started looking into INDI - it was very clear that I can build a lot with it. However, it wasn't clear what exactly I can build. I think it would be nice to have some page where new INDI-users would land and see the full picture of all pieces connected, something like quick start guide. Say some graphics displaying mount, OTA with main camera, guiding scope with auto guiding camera, filter wheel, motorized auto-focuser, OTA flip caps.. - how it is all connected to computer/RPI with INDI-server and then how it is controlled via KStars/Ekos. Some high level view diagram but with reference that you can connect lots of devices available on the market. I see INDI as tool to make all astrophotography equipment to be Lego-pieces, where you can build different setups. Also, users should get understanding that things like imaging sessions planner, Go-To, plate-solving, polar alignment assistance, auto-guiding, meridian flip, auto-focus and etc - all these things are already solved and automated by INDI.