Well, like I said in my last post... I think the palace is just too "small scale" to really fit into the game as something that acts as or interacts with gameplay mechanic..
No more "small scale" than leader/unit animations.
In terms of interaction, the best role I can see for it is as a History (sort of like a condensed "replay")...which works well with some features [Government Legacy bonuses, Districts, possibly Great People)
Major events in your history would show up there
-Governments is easy (something based on current government and legacy bonuses you have now)
-Civs you eliminated/or captured their capital
-Religions founded/present in your empire (not just the sign, but possibly the beliefs)
-Great People (depending on how many you get in a game)
-Luxuries/Strategic Resources that you had a lot of over your history
-Specialty Districts that you have a lot of (proportionately...throughout history)
...have the game remember it at the end of each era, and you have 7 "pictures" that show your history (probably a map as well off to the side)
It also runs into the problem that the idea of a palace as the "leader room" basically loses its meaning in the midgame.
Not really, most nations have a Capitol building of some type, at least one of the "leaders" of any decently sized modern nation has some type of a "palace".
Although Exactly how it should be implemented palace/throne room/"capital city monument area"-like in the CTP game would need to be worked out to properly show what you wanted to show.