I agree that OP should not try to take on all shopping experiences. That is a gigantic undertaking, trust me I am about to do it myself. What I am suggesting is to pick one channel , grocery store, club store, drug store, etc and blow that experience out and how a new cart can make it better. To be honest designing a new shopping cart with a few bells and whistles I don’t find to be that strong. I personally think my cart is fine and don’t really see the need for an upgrade unless it is providing a greater value or improving the shopping experience. Even if you improve it for the retailer it still has to provide a consumer value or the retailer will not adopt it.
Like I mentioned before, a consumer experience approach will show greater thinking which will create a stronger portfolio project. There are a lot of design student out there that can create a cool shopping cart, it is you job to show us what your point of view is on the need for the consumer. Why nt make tat as strong as possible?
J