I hadn't really thought about AR Ecommerce but just imagine visiting IKEA, picking a product and IKEA placing it over your phone's view of the room you want to put it in? Accurate sizing could be difficult but all of their imagery is already CGI.
White balance could be adjusted for automatically, perspective calculated from edges of the room etc. I think you would need to allow manual overides so that the shopper can fix problems due to the software not calculating what is going on in the view but it could be very cool. This would require a lot more AI than I think is currently used in a lot of these applications of AR.
I don't think I would trust it for fashion, I reject a lot of clothes due to poor quality/thin fabric or because I'm curvy and even the right sized clothing often isn't the right shape. Clothes shopping is a very tactile experience. I think it could work for generic T-Shirt places like Spreadshirt though.
The closest thing I have seen is ASOS's catwalk videos, do they still do those?