Ecommerce store

This is my first post and I'm a Unity noob.

I was going to create an ecommerce app for a physical product that I am launching, but decided that Unity would be better for the following reasons:

1. load times - I don't mind a 5-10 second load time as we are creating a cooperative type of commerce, i.e. users own the company and therefore shouldn't mind a few seconds to get into the experience

2. battery life - I know a game engine is constantly running as opposed to an event-driven app engine, but our users will not be spending so much time inside our experience that this should matter too much

The upside of using Unity will be a uniquely gamified commerce experience (leaderboards, level up, missions, etc.) . So this post is not too long, I won't go further into that now.

My main questions are:

1. Shopify has just launched something called the Unity Buy SDK. It allows developers to sell physical products inside a Unity game. I do not think the Shopify solution will be robust enough as I need an ability for users to sort and filter search results. More significantly, I want users to have their own storefront (think marketplaces like Ebay, Etsy, Amazon). Is there a way for me to setup an ecommerce platform with robust features like this and importantly – users will not need to leave the experience/environment I'm creating?

2. My product is a "platform product". In other words, it is a product that users can customize with their own designs. Though my product is not a t-shirt, we can use that for an example. I would like to create an interface where users can create or upload their own designs to a personal storefront in our marketplace. If it sells, we manufacture/ship the product and the creator gets paid. This will require the user to create a "sellers" account, which I'm thinking could be the same account that a regular store shopper sets up to make a purchase, but also have a bank account attached to receive funds from any product sales and monthly reports on how their store is doing. Is it possible to create something like this with Unity?