such thing like “too many provinces”… is what will make all maps, MKJ and Polish included, unplayable.
While the number of provinces you can request in a war will remain the same, the amount of BB you gain for conquering provinces will remain the same, the number of colonies you can plant will remain the same, the number of provinces you can convert will remain the same, and the time to do it all will remain the same, the new maps will have double amount of provinces or more. So people will be able to achieve half, and the AI probably much less than half. I don't even want to think what will happen to AGCEEP if moved to one of these maps. People will try once or perhaps twice and will go back to the default map "en masse".
The moddable maps offered the opportunity to fix some serious mistakes and perhaps increase the number of provinces up to 10%. A 50% increase is a serious overkill, as time will demonstrate. Not that I want to discourage you. The maps look beautiful.