Player-choice-specific faction, visual, and audio adaption.

I'm not a 4x expert and I'm new to the game, so forgive me if I misrepresent it somehow. Anyway...

I think the visuals and audio should reflect the assumed tone of the player's actions an intentions. I'll elaborate.

Say I'm playing as the United Empire with a heavy emphasis on military, conquest, economic growth, and nationalism. In a system's infancy it looks perfectly normal. Further into the game, after noticing my choices -- be they war and invasion, certain laws, technologies researched, diplomatic and quest choices -- the game may implement certain visual and audio changes on the dominating planets and systems such as a stentorian voice giving a propaganda-filled speech over a loud speaker, large satellites beaming advertisements to encourage consumerism, a proud and chauvinist national anthem replacing the normal soundtrack when zoomed into the system map, you get it. 

Now say I have some far-off system with a conflicting ideology (pacifism, ecology, whatever) that I've either encouraged or failed to squash. That planet or system may have a completely different tone. Maybe instead of the blaring anthem, an ecologist system may have changed almost nothing at all because they don't want to dominate nature.

The point of all this is twofold:

1. To give our systems a sense of place and character and to allow the player to easily recognize what kind of system or planet they're looking at without having to navigate any menus.

2. To make the player's faction more malleable, so that they bend to the player's choices and not necessarily the other way around. So, to some degree, the player feels less like they're piloting a faction and going through the motions, making the choices sound like what their faction would make, and more like they're contributing to the faction's identity through their choices. This makes that faction feel more unique to the player in every single game. If a player thinks "I like this faction, but I wish they were a bit more like this," they can do that. It may also add more variety to multiplayer, so that when whatever faction shows up they don't think "Welp, I know where this is going. Better build up my defenses."

These adaptations don't necessarily have to be in the player's face or take up a lot of screen real-estate or make the game more demanding of a player's hardware, but I think something like what I've mentioned would add to the game's character and replayability. Right now the only indications we have of what faction we're playing, or of that faction's character, are the hero portraits and ship architecture (unless I'm forgetting or missing something, which I may be. I'm new. Don't kill me.)