In my local Aldi the scales are enormous - you can definitely fit a full trolley full of groceries on the scales. A local Tescos has two kinds - one set of self checkouts with small scales for people with baskets only, and one with huge scales for people with trolleys. They look like this, you can fit everything on it: https://ninanco.com/wp-content/uploads/2019/06/4a-blurred-11...

In other words - this is a solved problem.