If the aim is to curb monopoly powers of Amazon etc this would be disastrously counterproductive

When Joe's Custom Bike shop isn't allowed to be a manufacturer and a retailer of someone else's bike equipment, the customer is going to go to Amazon or Wal Mart to buy it. And retail giants, buoyed by the government killing half their competitors, will still find a way of squeezing their suppliers and funnelling sales data to preferred suppliers or related entities.