Well, since then my game has undergone enormous changes, and very little of the Risk Europe rules still remain. I'm not exactly sure what I did and didn't use from the original game, but I believe I scrapped the city bonuses, and added God-Kings as an extra unit, which could only be recruited and defeated under certain circumstances.
Since then I have:
• Changed the combat system
• Changed victory conditions (play 6-8 rounds and then count victory points)
• Added different kinds of resources (Gold & Prayers)
• Added different kinds of buildings (Capitals, cities, castles and temples)
• Added nation bonuses (Reduced building cost, combat bonuses etc.)
• Added diplomacy (At war, At Peace, Allies, each with their own pros and cons)
And probably a lot more that I can't think of right now