That sort of thing could really only work with a "licensed" e-commerce solution that you'd install as software on your own server, where that software controls the entire shopping and purchase process on your site from start to finish, including your page layout, product listings and checkout payments.
Since our "hosted" service just adds our cart buttons and cart to your own site which you maintain however you wish, we don't even control the purchase process every step of the way, and buyers would already have an account with the payment processor (e.g. PayPal) that they'd log into for checkout, there's really no practical and useful way for us implement return-customer accounts with wishlists, etc.