There are some "formable nation" ( like Indochina ) dont giving core on all states inside the new nation border. I think because the map in game is different from the Vanilla, so the script need some adjustment.

Other formable nations ( needed in game ) can be:

Italian Empire: Italy, Greece ( execpt Thrace ), Albania, Adriatic's coastline, Savoy, Corsica, Tunisia, Egypt, Sudan, Malta, Cyprus, and African Horn

Napoleonic Empire: French, Belgium, Luxembourg, Netherlands (except Friesland ), Piedmont, Moselland, Rhineland.

Insulandia: Dutch East Indies, British Malaya, Philippines, Papua, Bismark, Solomon Islands