score:7
Can a Patron Saint formally declared as such by a pope be replaced?
Generally speaking Patron Saints are rarely declared as such by Rome (Pope). When a pope decides to appoint a saint to the patronage of someone or something, he could theoretically change the patronage to another saint. However I have never ever known this to be done and doubt it will ever be done.
Fact of the matter that some professions, counties and individuals may have several patron saints for the same thing.
For example the patron saints for fishermen are as follows:
Andrew the Apostle
Anthony of Padua
Benno of Meissen
Budoc of Brittany
Gundisalvus of Lagos
Nicholas of Myra
Our Lady of Mount Carmel
Our Lady of Salambao
Peter Gonzales
Peter the Apostle
Zeno of Verona
Thus Rome would simply add another Patron Saint to the list than removing one for another.