And they already were doing so... this is the alluring concept of being a Roman. Since Caracalla granted all free men and women citizenship, being a Roman meant being a citizen, thus exapnding the concept to a national one, outside of language, religion, and heritage. The Romans later made the focus more on following the established church, but that did not make one a non-citizen for not being a subscriber to the universal church. Turks, Bulgarians, Armenians, Albanians, Arabs, Egyptians, Syrians, Hellenes, all were Romans. All were bound by laws and had the use of the courts for justice. The emperor was their emperor and the empire theirs. The Republic was a public thing, a government and civilisation held in the commons. They were one nation, with one emperor. Something they guarded jealously and their neighbours never understood. Unfortunately this unique quality of worldview, their ideology, made them into total snobs.