unfortunately, this can't be replicated for a mom and dads corner store, since the overhead is gonna be so much bigger than their revenue would allow.

...unless SaaS providers of this kind of service exists, and the fixed overhead costs bourne by a lot of small shops together.

It can, not easily but most of the management needed by said corner store can be automated using SaaS. This approach combined with the app AND the point-of-sales data you can provide to smaller stores by doing so offer benefits for everyone. And the overhead won't be that big for the SaaS start-up as soon as economies of scale kick in IMO.