Dracosolon
Emperor
To come back to a proposal I made some time ago, I think if we wanted to give civilizations more incentives to move their Palace (and for a player to reconsider where it should be located) it might be interesting for new eras to unlock a new Palace building with slightly more powerful bonuses. Though this wouldn't really fit what you're talking about since this would happen across eras, instead of representing a division of power inherent to an era.
It seems to me that if we wanted to simulate what you're talking about, then having Republic (or another civic) negate the bonus provided by the Palace to the capital city, in exchange for a bonus in every city, might be better at modeling this. At least I'd rather have this than rebuilding my Palace several times per era - though I would be okay with a mechanic where instead the Palace randomly switches between your different core cities.
Problem is that this wouldn't really fit with more centralized Republic civs like early Rome or Netherlands. But perhaps this shouldn't be tied to a civic: instead some specific Republic civs like Italy or Greece might start with a "City-States" status that gives a per-city bonus but negates the Palace bonus. This status will eventually be lost: could be when the civ switches out of Republic, when it builds a new Palace (in which case my first idea about era Palaces might be useful), or maybe both. The idea of a civic-like status that some civs start with and that will be lost later reminds me of previous discussions about nomad civs, too. Maybe the two mechanics could work somewhat similarly on that front.
Though all of this seems a bit complicated/overly finicky just to model city-states (especially since currently a Palace doesn't give much of a bonus to its specific city, having instead a much more important role for the maintenance of nearby cities, something which wouldn't be affected by switching your capital between different core cities). I'm not sure what would be added by this besides realism (something Civ IV struggles with when representing lack of political unity anyway).
It seems to me that if we wanted to simulate what you're talking about, then having Republic (or another civic) negate the bonus provided by the Palace to the capital city, in exchange for a bonus in every city, might be better at modeling this. At least I'd rather have this than rebuilding my Palace several times per era - though I would be okay with a mechanic where instead the Palace randomly switches between your different core cities.
Problem is that this wouldn't really fit with more centralized Republic civs like early Rome or Netherlands. But perhaps this shouldn't be tied to a civic: instead some specific Republic civs like Italy or Greece might start with a "City-States" status that gives a per-city bonus but negates the Palace bonus. This status will eventually be lost: could be when the civ switches out of Republic, when it builds a new Palace (in which case my first idea about era Palaces might be useful), or maybe both. The idea of a civic-like status that some civs start with and that will be lost later reminds me of previous discussions about nomad civs, too. Maybe the two mechanics could work somewhat similarly on that front.
Though all of this seems a bit complicated/overly finicky just to model city-states (especially since currently a Palace doesn't give much of a bonus to its specific city, having instead a much more important role for the maintenance of nearby cities, something which wouldn't be affected by switching your capital between different core cities). I'm not sure what would be added by this besides realism (something Civ IV struggles with when representing lack of political unity anyway).