The speed also depends on the unit type composing the stack...maybe checking the slow unit speeds (cannons generally) would help. Fix that, then fix others accordingly and u're done. While probably it would be easy to fix the number of days for movements, the only thing move-wise missing in the engine is the lack of calculation of days needed to put a city under control and the eventual loss of men coming from this process.
If you by chance happened to send a raider into enemy territory and see 3 cities undefended, you could take them all in a single turn...entering a region with a settlement or without, is virtually the same and no days are lost to put any city under control. Ideally, to control a city you'd need some days, no (the bigger the city the more time it should take) ?
Also, you'd need to turn some of your military personnel into police forces to start collecting taxes and so on...these things are totally missing unfortunately.
We ain't going down!