The problem here arise in that, if I'm not mistaken, that 2nd level Cure Wounds still counts against the number of spells you can prepare. That way, you are limiting your spell selection just to have Cure Wounds at both first and second level, taking two slots when it should only take one. Maybe I'm mistaken, didn't messed a lot with it. If I'm wrong, feel free to correct me.
That shouldn't be happening. Spells are prepared individually. As the PHB states:
You prepare the list of wizard spells that are available for you to cast. To do so, choose a number of wizard spells from your spellbook equal to your Intelligence modifier + your wizard level (minimum of one spell). The spells must be of a level for which you have spell slots.
So Cure Wounds would be only one prepared spell. Otherwise no one would take Burning Hands once they reached level 12 or so.
