That's an interesting interpretation, but I'm not sure how your class came up with it. I don't think the script supports Rick as a "gangster type who has led a life of crime."
Captain Renault: In 1935, you ran guns to Ethiopia. In 1936, you fought in Spain, on the Loyalist side.
Rick: I got well paid for it on both occasions.
Captain Renault: The winning side would have paid you much better.
In other words, Rick has a history of fighting against Fascism, and has to leave Paris when the Nazis invade because of his anti-Fascist record. He drops out of the fight due to his bitterness and disillusionment over Ilsa, but his idealism is renewed by the end of the movie.
So: he's a good guy who withdraws into a hard shell of cynicism for about a year and a half (but even in Casablanca he covertly helps people, like the young bride who is going to have to sleep with Renault until Rick fixes the roulette wheel to give the couple enough money to pay cash for their exit papers).