As far as story and character? Of course it can.He has one of the most tragic back stories out there and plenty of arcs and villains of his own. The script they have now alone is almost perfect. The blurring of morality is what would make the character actually stand out in this decade. Not really a character out there like him. Grabbing a new audience is the issue. But every new property has to deal with that. Mystique also has plenty to ride on for a solo if they really want one. After being the lead X girl for two films it's not that out there of an idea. I think it may be overkill for the character and franchise, and personally would rather they focus elsewhere. But there is plenty of material to work with given her new leading role in the films and her solo comic.