That's a brilliant idea! Do you mind if I propose it? Nah, they'll never believe I came up with it.
On the other hand, something like 'archive.stackexchange.com' would be a good place for all the questions from discontinued SE sites. Maybe we could tag them with the names of their old sites? And have them all closed too? And disallow everyone from logging into the site or creating an account? Yup, I left the whole idea of the SE network in the dust right there ;)