One thing you could do, to keep the number of provinces on a reasonable level is to make some kind of list of all the new provinces, and then people will have to defend each province they would like to see in the game.
As I haven't tried this map yet I don't know how it's changing the game, but as the game is made for the map that's in vanilla, with below 1600 land provinces (don't know the exact number), it might cause some balance issues with an 1539 OE that's increased from e.g. 25 provinces (just random numbers, both of them) to 50 provinces.
Some provinces are definately needed, the HRE needs more provinces than in vanilla, Portugal and Denmark needs more provinces and ROTW, especially Asia needs a lot of new provinces. But that e.g. Greece is increased from 7 to 13 provinces looks dangerous to me (if Greece wasn't particularly difficult to hold in the era, I don't know).