Allow Commendations of Valor to be traded in for quarter hearts of wood of the appropriate type. Then, also sell these quarter hearts on the store as well for one quarter the price of a full heart. Make the quarter hearts clickable, so that people can craft their full heart.
In doing this, you allow a mix of grind and store purchase for those who think the current heart system is too expensive on the store, but are willing to spend some money. This also helps VIPs to some extent.