For a long time, I've argued we need leaf certificates to be double signable. That way there can be two chains of trust for a website. Then dropping a CA doesn'

For a long time, I've argued we need leaf certificates to be double signable. That way there can be two chains of trust for a website. Then dropping a CA doesn't matter much, since all serious parties should have multiply signed paths to various roots of trust. Hence we solve the problem of CAs becoming to big to fail. The current way cross-signing works is almost an accident, and only works for intermediate certificates. Because the 'signing cert' is looked up by name. An intermediate cert can be published twice with the same name, same key, but different signatures and signing cert. Hence doing this for a leaf certificate would mean 'just get two certificates'.