I tried it with Austria, and it's even more OP in the scenario. At the end of the game, I bought off EVERY SINGLE city-state on the map because of such a strong economy. Taking off the Byzantines with them and allying and buying the Vatican is worth a big chunk of points. During my last turn, I had conquered the whole Byzantium, Turkey and France, half of the Ayyubids and my empire extended from north Spain, France, Italy, Austria, Germany, Poland, Hungary, rest of eastern europe, Turkey, middle east and Arabia, with a few cities on Tunisia and Malta. It's SERIOUSLY overpowered.
I played on prince though, it was my first GnK scenario and I soon moved on to King. Russia was crashed by the mongols quite early in the game, and England kept fighting the Netherlands for some reason.
In general, I won every single HRE, sailed all the available caravels to west (from my rush bought Lisbon. It was seriously made with the only purpose of being married with Austria), conquered 3 and a half major civs and had more than 12 thousand score. I'm right sure it couldn't be done in higher difficulties, but it seemed way easy to win as them.