Black Adam is problematic because it goes to the sword between good and evil, and as easy as a time it acts as a "hero" and JSA member in another it may be a threat of global proportions that would not hesitate to use power lethal and kill even the most brutal ways possible their "former companions team" as he did in "World War III". Who knows his former sidekick Osiris is not a better choice to represent Khandaq? Especially because Black Adam would suffer from the same problem of Aquaman in Justice League Unlimited ... Since he was the leader of his nation he would have administrative problems to solve so could not be a permanent member of the Global Guardians. And I think you could have included a superhero representative of Thanagar on Earth, as well as a New God of New Genesis, one of the immortal monks of Nanda Parbat, and a representative of the Lantern Corps as well as Jemm Son of Saturn and Amethyst Princess of Gemworld do you think?