in-app purchase, or not? the choice is yours

I would love to see a system where the customer can buy in-app purchases, directly from iTunes. For example, they go to Rolando 2, and they want to buy the entire game at once (I know several people who do so). When the costumer should be able to check checkboxes of in-app purchase packs.

There was a solution for this, that was to make 2 apps, one for in-app purchases, and one for the entire game. Though, when every developer does this, the app-store gets really messed up. I hope you consider this idea.