sometimes i don't know what kind of wizard my character is going to be until i play and get to know the character.
my suggestion is to put npcs in the major magic gathering hubs, or special findable magic books, that allow the wizard character to commit to a magic specialty after character creation. per the current standard, it would be a final and irreversible decision while granting all the boons and cons as if taken at the creation screen. this would allow wizards to take up a specialty after creation if RP has swayed them into a certain field.