I think Civs should evolve.
So, for example, if the Spanish reach such level (for the HC), they would become Argentinians or even Mexicans and the Home City would change.
The Portuguese would become Brazilians, the HC would be Rio de Janeiro and the leader would be Dom Pedro I.
The British would become Canadense people.
The French would become Quebec.
The Dutch, well, I'm not sure, maybe suriname??
The Ottomans, Germans and Russians would just evolve into something new, but no other Civ...