The only real life thing I miss is migrations.
But the happiness system ends up doing something that looks like it, so no complaints.
On the other hand, not exactly a real life thing, but I was dreaming on a mechanic that mimics centralization.
For example, I could directly control all of my cities, all of my armies, and play the tyrant. Or I could set a few cities free from my rule, but still belonging to the empire and contributing to our wealth and manpower. Or even grant them complete autonomy, so they are free to act on their own, but always allied to me.
Wait, wait. I know. There's puppet cities and vassals for that. But as they are now, we can only have a puppet from a conquered city and we can only have a vassal from a vanquished country.
I'm talking about having the option to decide whether a new city is gonna be puppet or controlled, of having the option to create a new vassal out of our own cities, a vassal who will not attempt to loose free.
I'm talking about reversing any of those statuses as we see fit, turning puppets into controlled cities, and vassal cities into owned cities at will.
Well, maybe with some restrictions.
In such scenario, a player could be regarded as a tyrant when most of his cities are owned, a king/president, when most of them are puppets, or an emperor when most of them are vassals.
The less the player controls, the harder it is to deploy strategies, but also the easier to manage. If the country is faring well, I could relax and let the AI handle the hard work for a while.