Will Sanju make crime pay?

Yes
Sanjay Dutt is an artist and he should have free reign on choosing what movies to do and what characters to play - if both he and his director think that he is the best man for the role, then why shouldn't he? He's not the conscience keeper of Bollywood nor should he be deterred from playing the role of a prisoner just because he was once in prison. Perhaps his own experience will bring sensitivity to his acting. As long as the movie doesn't promote murder (which it morally shouldn't), he should go ahead.

No
Of all the actors in B'wood, Sanjay Dutt and Salman should avoid playing villains or prisoners, especially those as unrepentant as Charles Sobhraj. Isn't real-life prison term enough for Sanju, that he is volunteering to play out more on screen!? Additionally, Charles is unrepentant - won't that send the wrong message to his fans (that he's forgotten the trauma of his jailed days!)? We prefer to watch him play Munnabhai - a big don with a heart of gold is far more attractive than bad boy turned murderer!