Lithuania would be a nice addition, but I still think the Abbassids would be the best choice atm as, many have pointed out, there is a major power vacuum in that part of the map. Based in Baghdad they could expand outwards and become a major force in the region, making it an important area rather then just a forgotten corner of the map dominated by the factions nearest.
Malta would be a nice region, as it was important historically. As was Adrianople.
Wonders of the world again would be sweet. Maybe not as powerful as they were in Rome, but still something to value controlling.
But yeah bug fixes and balancing should be first. Many have suggested reducing rather then eliminating the new traits, which would be fine.