For the sicilians I would suggest a bonus that give them +100 starting stone, since they are so vulnerable to Trush strategies. In fact, only one tower form the enemy is enough to force the sicilians to build a donjon, and to burn all their stone, so that they need to gather more of it for TCs in the castle age. While the enemy can simply send 3 of the forward vills to gather 10 stone each, and it’s enaugh for at least a TC.
Another buff may be one to their monastery, both for balance and historical purposes I don’t get why the sicilians have terrible a monastery. I think that they simply should have redeption and block printing, and maybe even atonement. Their bonus aren’t that crazy, but at least they could have a flexible tech tree. The monastery is what keeps them behind the most in this aspect.