I think, it is a very good method of having a corruption system which isn't unfun. The fun/unfun aspect of game mechanics seems to be a major guideline for the programmers, which is in itself a good thing (as long as the game retains a certain level of complexity).
Of course, it could have been done in a better way (in my opinion), but then again, my ideal corruption model also wouldn't be everyones perfect corruption model.
For one, I would have liked to make the civics options have a large influence on the level of corruption. Things like a centrally organised government vs a decentralised government, representation vs absolute rule, treatment of conquered cities (assimilation vs slavery), level of freedom of religion and other options. Also technologies that improved communication should greatly influence corruption. Technologies like radio, railroads, television and a national postal service should help increase the effectiveness of a government. This would mean that early in the game, large empires would be very difficult to control and as technology opens up new civics options and new communication methods, larger empires become more feasible.
