Build-a-Box Subscription

I’m looking to build an eCommerce solution that allows customers to purchase a build-a-box type subscription. There are three different levels. Each level has specific restrictions to the number of things they can buy as part of their membership. For example, you can buy three vegetables, two types of meat, and one dairy item. Each week, they’d be required to go in and update their selections and/or add-on to their weekly subscription. I’m hoping someone can shed light on how the user workflow should be built. Currently, I was going to have people buy a Subscription product, which would grant them membership access to that level, and then they would add a composite product to their cart. But it seems like there are soo many steps, that it has to be an easier way. Plus, how do we “reset” their cart each week to force them to log in and fill it with that week’s offerings. HELP!