when you extend your countries, you can decide which empire is the primary one and you can switch.
the condition is, that the one you have chosen, is extended to the last day of membership.
anyway, for people who play for a long time and already knew about the extension of countries, including you (Inanna), all this is not relevant.
in both ways, the cost is exactly the same.
we can switch a player to the new system but there is no way back so we never advertised it.