My wife has been away this week and I've solo tested the game several times to try out a new action selection system. Instead of the prefect abilities laid out in a 4x2 grid, they're now arranged in a 3x3 grid (Raid and Conquer functions are now split over 2 prefects). Instead of choosing one action each turn, you choose two, but they have to be adjacent in the grid. It speeds things up a bit, because naturally related actions (eg populate-produce, or migrate-conquer) are placed together in the grid.
I've also managed to streamline some of the bureacracy, by giving each player an abacus to track resources, by having achievement token payouts hard-wired into the action display, and by cleaning up the way events work.
And, some of the fiddly rules are removed or relocated. One of the biggest culprits was the definition of a "trade route". Now, it's simply a city or capital adjacent to a foreign city or capital. The details about citizens in an isolated city or foreign citizens in your capital is removed, BUT the effect is still present in this way: when you produce and receive achievement tokens for your trade routes, if another player has a citizen in one of your cities or capital, he gets a token too. Several other systems have similarly been cleaned up.
My solo tests seem to be taking about an hour per epoch for 4 players, and that's with me playing all 4 positions. Real players in all 4 seats might be able to go much faster. An hour per player isn't too bad but 45 minutes per player would be even better.