The location of the memorial should be something the community agrees on but not behind any permit locked systems if possible. ( a lot like the idea of in a black hole system )
After reading the messages so far, a nice scientific beacon / mega ship studying black holes would be nice.
I agree with the petition, but I would suggest FDev hold off with renaming a Black Hole (or renaming/building a Space Station) for a while. It is likely (in my opinion) that the Astronomical Societies around the World will want to honour him, and they may well also feel that renaming a Black Hole in his memory would be a fitting tribute. If this were to happen FDev could then follow their lead.
I would very much like to see Stephen Hawking honored with something in game. He was an amazing person, not only defying the odds given to him with his medical condition, but also giving a massive contribution to science and knowledge that could never be overstated.