Ideally, this suit will be a trigger for Congress to regulate. The historical precedent is last century’s retail monopoly A&P (yes the now defunct Great Atlantic & Pacific Tea company, who were Wal*Mart scale at their height). Which triggered the still in force (but not enforced) Robinson Patman Act (of 1936), to level the playing field in retailer/supplier relations.
And I think this case also has echoes of various FTC Anti-trust actions against IBM in the mainframe days, where you have a dominant supplier (IBM) and a number of smaller players (the “BUNCH” -Burroughs, Univac, NCR, Control Data, Honeywell), with some systemic remedies to level the playing field. Maybe a spin out of AWS (and platform services like advertising, payments?) to prevent future cross-subsidies
I think a side helping of FTC action in the advertising space (Google & Amazon) is overdue
Re: Shopify POS The problem with POS is that you get diminishing returns to roll out internationally. The challenge is the need to fiscalise the POS specifically for many international markets (Toshiba including the former IBM business is one of a select few that do). Also PSP/PED supply can be regionalised (and you need to certify each hardware model of PED, potentially PED/PSP combinations, to operate). Also integration to POS hardware can be challenging (especially self-service/scan as you shop)