Personally I enjoy the way castle blood is now.
Adding things like that just complicates it. And I do know what the hell I am talking about. What other upgrades can you get? Not too many, I can only think of Civ's Advanced Church upgrades, which you may be able to incorporate, that is a good idea, that way the church is less useless
. Giving each civ its own Advanced Church does not make sense because some of the upgrades are for Eco, like the Dutch coin thing that gives you 2 more banks. But if you could find the individual upgrades and give them out for buyildings razed that would add another level to the map.