Rebels or Loyalists

[Martok]

But we won't actually be able to change factions trough this mechanism will we? For example play the Thirteen Colonies if they rebel from Britain?

Actually, I believe that's precisely what happens if/when the U.S. emerge -- you get the choice to either play as the Americans or continue playing as the British (or whichever faction happens to own the Colonies at the time). However, I do believe that is the exception to the rule.

I thought it meant more if you change between the three government types, on a faction-wide scale.

That's my understanding as well -- the Thirteen Colonies appears to be a special situation that probably won't apply anywhere else. Normally, if you have a revolution/rebellion on your hands and you have to choose between backing the Loyalists or Revolutionaries, it's across the entire faction.