As one option, make some cards worth variable points, at the narrator's discretion, to emulate more powerful abilities.

For example, after playing for some time, a wizard's Wizardly Powers card could be upgraded to potentially providing 2 points per card to emulate his increasing skill as a wizard. Later, more upgrades could increase it further.

Another option to emulate increasing characters' abilities would be to issue them more cards and increase their card limit per scene.

One way keeps the choice in the hands of the narrator, the other in the hands of the player.