For the HRE, I have an idea. You can take the piety concept from the game and once a Catholic civilization has X amount of piety, the HRE forms. The HRE is destroyed when the current emperor's civilization is destroyed (IRL, by Napoleon in 1806). When you discover a certain tech, you can build a wonder called Bundestag. When the wonder is complete, the HRE is dissolved if it still exists and the German Confederation is formed. The GC could be similar to the HRE but has more choices and resolutions. Although historically inaccurate, the GC will last for the rest of the game.